SU1685917A1 - Method for obtaining ester hardener for liquid glass moulding mixtures - Google Patents

Abstract

The invention relates to esters, in particular the preparation of an ester curing agent for liquid glass molding compounds in a linear production. Tset - improving the quality of hardener. The process is carried out by the esterification of ethylene glycol with acetic acid in the presence of orthophosphoric acid at 100-180 ° C and atmospheric pressure in the presence of 5-15% by weight of propionic acid, calculated on the initial ethylene glycol with simultaneous distillation of water from the reaction zone. Ether provides a reduction in the curing process time, an increase in the initial strength of the molding sand by 1.5–4 times and a decrease in the vitality of the molding sand by more than 10 times as compared with the known hardener. 1 tab.

Description

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The invention relates to the technology of basic organic synthesis, in particular, to the preparation of ethylene glycol esters used in curing liquid glass mixtures in linear production.

The aim of the invention is to improve the quality of the hardener, resulting in a reduction in the curing time and an increase in the initial strength of the molding sands.

The essence of the proposed method is illustrated by examples of the preparation of a hardener and its use for its intended purpose.

Examples 1-11. To obtain an ester hardener, 248 g of ethylene glycol, 480 g of acetic acid, 16.5 g of propionic acid, and 2.5 g of orthophosphoric acid are loaded into a round-bottomed glass flask with a capacity of 1 dm 3 (esterification) at a cube temperature of 170 ° C and atmospheric pressure. At the same time, the water formed is removed from the reaction zone by distillation as an azeotropic mixture with acetic and propionic acids using a distillation column (inner diameter 12 mm, height 100 cm, nozzle - glass rings with a diameter of 4 mm). The bottom product is an ester hardener in the amount of 648 g, which is a clear, uniform yellow liquid (opalescence is allowed). Physico-chemical properties of the product according to examples 1-11 are given in the table.

To obtain other samples of the ester hardener, the process is carried out under the conditions described above by varying the amount of propionic acid with respect to the initial ethylene glycol (see table).

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Examples 12-14. The hardener is prepared under the conditions of a known method by acetoxylation of ethylene glycol with acetic acid in the presence of toluene while simultaneously removing the reaction water from the reaction zone as an azeotropic mixture with toluene.

The table shows the comparative characteristics of the molding mixture with the addition of a hardener obtained by the known method.

Test the properties of the molding mixture. The ester hardeners prepared according to examples 1-14 are used for the preparation of compositions of liquid-glass molding sands.

To obtain a liquid molding sand mixture, quartz sand (100 May. H) is charged into a mixer apparatus suitable for mixing granular and pasty media. Then, while the mixer is in operation, an ester blender is poured into it (0.35 May. H), after the contents are stirred, the reactor takes 1-3 min. Mass of the R apparatus takes on a uniform flowing form. Liquid glass with a density of 1480 kg / m3 (3.5 parts per part) is introduced into the mixer. After 40-45 seconds of stirring, the mixture is ready for filling the forms. The mixture is then released from the mixer and standard specimens with a diameter of 50 mm and a height of 50 mm are made from it for testing compressive strength on a standard instrument. The survivability of the mixture is determined on a device whose action is based on measuring the resistance of cylindrical pptor in the volume of the mixture.

The table presents the results of the tests under identical conditions of the compositions of liquid-glass molding mixtures, which were prepared using the ester hardener obtained according to the proposed (examples 1-14) and known methods (examples 15-17).

From the above data, it follows that with a change in the ratio of propionic acid: ethylene glycol in the initial reaction mixture, the initial strength of the molding mixture increases significantly, while the survivability decreases abruptly. However, upon reaching this ratio of more than 15%, the initial strength of the molding sand is reduced while simultaneously reducing its vitality, which makes practical use of the molding sand impossible.

In addition, the presented results show that the proposed hardener provides an increase in the initial strength of the molding mixture by more than 10 times compared with the results of the application of the known hardener.

Claims (1)

Invention Formula The method of obtaining the ester hardener of liquid glass molding mixtures by esterification with ethylene glycol with acetic acid in the presence of orthophosphoric acid at 100-180 ° C, atmospheric pressure with simultaneous distillation of water from the reaction zone, characterized in that, in order to improve the quality of the curing agent, the process is carried out in the presence of 5-15 wt.% Propionic acid in the calculation of the original ethylene glycol. Note. In Examples 11-13, the esterification is carried out with a change in temperature in the reaction zone: Example 11 at 100 ° C, Example 12 at 150 ° C and Example 13 at 180 ° C. Examples 15-17 are given for hardener, obtained by a known method, Table continuation