CS271904B1 - Method of epoxy resins' low-viscous reactive solvent preparation - Google Patents

Abstract

The solution concerns the use of a low-viscous reactive dissolvent of epoxide resins, which is prepared by boiling a mixture of cyclo aliphatic ketones with monoethanolamine in a molecular ratio of 1 : 1 during azeotropic water removal by means of cyclohexane or toluene, whereupon cyclohexane or toluene is distilled from the reaction mixture at a normal pressure, overhead distillate at the pressure of 3.33 kPa to a temperature of 90 degrees C, while the mixture of 2,3 and 4-methylcyclohexanones and cyclohexanones with the content of ketones 90 to 99.5 percent by weight is understood by cycloaliphatic ketones.

Description

The invention relates to a process for preparing a low viscosity reactive solvent of epoxy resins based on cycloaliphatic ketone condensates with monoethanolamine,

In order to ensure good processability of epoxy resins, DC requires their lowest viscosity. This depends on the temperature, the relative molecular weight, its reactivity with the hardener, etc. In general, a reduction in viscosity can be achieved by adding low molecular weight substances. Organic solvents mostly volatilize 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. Low viscosity results in better processability and bubble escape from the composition, easier mold filling and higher filling. 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 lowest addition of reactive solvent is required. 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 acrylates, for example, a double bond reacts 4 times faster with amines than epoxy resins, thereby limiting the size of the possible casting or complicating the 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 mucosa. Acrylates also damage the respiratory mucosa by inhalation. The dangers of acrylates strongly depend on the molecular homogeneity of the acrylates; the liquid causes skin inflammations, especially during long-term exposure. Conventional Diana epoxides provide rigid, rigid, sometimes brittle materials by curing with conventional hardeners, which, in conjunction with materials with other bulk thermal expansion, have considerable internal stresses and often lead to cracking of the products. insufficient resistance to low temperatures, impact, etc. The use of reactive solvents usually provides flexibility.

We have now found that some of these problems can be solved by using a low viscosity reactive solvent of epoxy resins, obtainable by reacting cycloaliphatic ketones with ethanolamine at a molar ratio of 1: 1 in the presence of cyclohexane or toluene as azeotropic drainage solvent. / at normal pressure and the residue at a pressure of 3.33 kPa to 90 ° C. Cycloaliphatic ketones are understood to mean a technical mixture of 2,3 and 4-methylcyclohexanones and cyclohexanone with a ketone content of 90 to 99% by weight. The product is a pale brown to reddish brown liquid with slight turbidity and mild terpenic odor. By dissolving in the epoxy resin, the haze disappears completely. The amine number ranges from 350 to 390, the viscosity at 25 ° C ranges from 0.012 to 0.020 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 lower viscosity of epoxy resins, as well as health safety during longer handling of the compositions in which they are contained. The high proportion of molecules with reactive groups causes almost all molecules to enter the mass, which then has a low volatile component loss under thermal stress.

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). ketones, cyclohexane and cyclohexane (1% by weight each). Both qualities differ in the content of ketones in the said mixture from 70 to B6% by weight, the rest being methylcyclohexanol (mixture of isomers 2,3 and 4). More preferred is the use of a 2nd quality with a minimum, a ketone content of 83% by weight.

CS 271 904 Bl

Cyclohexanone should be low. 98.5 Atria.

Technical methylcyclohexanone or cyclohexanone is refluxed under azeotropic dewatering using cyclohexane or toluene until the theoretical amount of water is separated. The starting ketones are used with ethanolamine in a polar ratio of 1: 1 (calculated on the ketone content), the reaction proceeds quantitatively. After distilling off the solvent, a small portion of the ancestors was 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 the above ketones with ethanolamine, they will be of the same type for the products. The composition of the reaction mixture is not known, nor is the procedure by which the complicated reaction mixture could be analyzed.

Example 1

A mixture of 270 g (2 moles) of industrial methylcyclohexanone with a ketone content of 83% by weight. 196 g (2 moles) of cyclohexanone (99%) and 244 g (4 moles) of ethanolamine are boiled under azeotropic dewatering using cyclohexane (150 g). The reaction is complete after 72 g of water have been separated off after approx

For 2.5 h. At normal pressure until most of cyclohexane, then the residue under a pressure of 3.33 kP to 85 _Q C to give 596 g of product pink color with a slight haze and a mild aroma terpenic Amine number: 370.1 mg KOH / g , viscosity at 25 ° C: 0.019 Pa.sec. 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 a product having a viscosity of 3.2 Pa.s / 25 ° C.

Example 2

A mixture of 392 g (4 mol) of cyclohexanone (99%) and 244 g (4 mol) of ethanolamine is boiled under azeotropic dewatering with 150 g of cyclohexane. Further procedure of Example 1 yielded 557 g of a light brown product with a slight haze, a mild terpenic odor.

Amine number: 395 mg KOH / 1 g, viscosity: 0.15 / 25 ° C. Homogenization of 90 g of an 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 3.05 Pa.s / 25 ° C.

Claims (1)

A process for the preparation of a low viscosity reactive solvent of epoxy resins characterized by boiling a 1: 1 molar ratio of cycloaliphatic ketones with monoethanolamine under azeotropic dewatering with cyclohexane or toluene, after which cyclohexane and / or toluene are distilled off under normal pressure. at a pressure of 10 psig to 90 ° C, wherein cycloaliphatic ketones are understood to mean a mixture of 2,3 and 4-methylcyclohexanones, cyclohexanone and mixtures thereof with a ketone content of 90 to 99.5% by weight.