PRODUCTION OF POLYESTER BASED ON ADIPIC ACID AND DETERMINATION OF OPTIMAL COMPONENT RATIO OF COMPONENTS

ABSTRACT

Recent research has focused on cross-modifying existing ones rather than creating new ones. As a result, hybrid substances with complex properties are obtained. For this purpose, the use of mainly thermoplastic oligomers is important. These include polyesters derived from different molecular ratios of adipic acid (ADA) and diethylene glycol (DEG).

АННОТАЦИЯ

Последние исследования были сосредоточены на кросс-модификации существующих, а не на создании новых. В результате получают гибридные вещества со сложными свойствами. Для этой цели важно использование в основном термопластичных олигомеров. К ним относятся сложные полиэфиры, полученные из различных молекулярных соотношений адипиновой кислоты (ADC) и диэтиленгликоля (DEG).

Keywords: thermoplastic polyester; synthesis of polyesters; solubility of polyesters; selection of solvents; selection of sinkers; turbidimetric titration of polyesters; optical density indicators; polydispersity.

Ключевые слова: термопластичный полиэфир; синтез полиэфиров; растворимость полиэфиров; выбор растворителей; выбор осадителей; турбидиметрическое титрование полиэфиров; покозатель оптической плотности; полидисперсность.

The polymolecular compound industry has been able to create new composite materials on a large scale due to a number of valuable properties of thermoplastic polyesters. In particular, as a result of their modification with traditional thermosetting oligomers, products with a molecular weight ten times higher are synthesized [1, 2].

Materials with high mechanical and impact strength can be obtained based on the composition of oligomers that retain phenolic groups and thermoplastic polyesters.  Modification of thermoplastic polyefires on the basis of protective oligomers furanovoy group plays an important role in the reception of radiation-resistant and high-temperature coatings [3, 4].

Method and materials: Adipic acid - (component A) GOST 10558-80; Diethylene glycol - (component B), GOST 10136-77; Zinc acetate - (catalyst), GOST 5823-78.

Synthesis of polyester based on ADA and DEG was carried out in the following sequence: 1 mol of adipic acid and 1.1 (1.5) mol of diethylene glycol cross-zinc-acetate catalyst and in a continuous medium of inert gas (nitrogen) at a temperature of 190-195°C. within 6 hours. After the completion of the reaction, the remaining water was distilled off in a vacuum [5, 6]. The molecular weights of the synthesized polyesters were studied by viscometry. The solubility and structure of polyesters were studied by turbidimetric titration [7, 8, 9].

Results and their discussion: In today's research, we will experimentally consider the effect of changing the molar ratios of the components of this polyester on their direct physical and chemical properties.

Experimentally (viscosimetry method) determined molecular masses of products, primarily synthesized on the basis of ADA and DEG at a ratio of 1: 1.1 and 1: 1.5 mol / mol. The obtained results are prollyustrirovany on the following graph (Fig. 1).

Figure 1. Dependence of molecular weight on molar ratios determined by viscometry

From the data in picture 1 above, it can be seen that the obtained substances have molecular weight indices: ADA and DEG in a ratio of 1:1.1 and 1:1.5 mol/mol, respectively: 1475 and 950 (MM). At the same time, an increase in the amount of DEG from 1.1 to 1.5 mol during the synthesis led to a decrease in the molecular weight of the product by almost 1.5 times.

This phenomenon can be explained as follows:

The polyester content in the 1:1.5 mol/mol ratio found contains more unreacted DEG molecules than in the 1:1.1 mol/mol ratio of the same product. This, in turn, results in a lower average molecular weight.

The next part of the research was continued by studying the structure and composition of both of the above polyester products. Turbidimetric titration was used as the most convenient method for this.

Since the turbidimetry method is based on the initial dissolution of oligomers and their precipitation, we were able to study the solubility of polyesters in a number of solvents by synthesizing ADA and DEG in ratios of 1:1.1 and 1:1.5 mol/mol. This made it possible to choose the most common solvents and precipitates for both systems (Table 1).

Table 1.

The most common solvents and precipitates for both systems

Table data. 1 show that the solubility in polyesters synthesized from 1:1.1 and 1:1.5 mole/mole ratios of ADC and DEG is practically the same. That is, both samples are insoluble in distilled water. Relatively poorly soluble in solvents such as ethyl alcohol and acetone. However, they showed good solubility in benzene.

These studies allowed us to select the solvents and precipitates required for turbidimetric titration. Thus, for all the studied systems, it is advisable to choose benzene as the main solvent, and distilled water as the precipitant.

Now we will continue our studies directly by turbidimetric titration of both samples. In this case, turbidimetric titration curves were obtained for polyesters synthesized on the basis of ADA and DEG in ratios of 1:1.1 mol/mol and 1:1.5 mol/mol (Fig. 2).

Figure 2. Optical density of 1% solutions of polyesterdependence on the amount of sediment

In this case: 1) ADA: polyether is synthesized in the ratio of DEG 1:1.1 mol/mol, the solvent is benzene; sediment - distilled water.

2) ADA: polyester synthesized in the ratio of DEG 1:1.5 mol/mol, solvent - benzene; sediment - distilled water.

The first curve in Fig. 2 refers to a 1% solution of polyester synthesized in a ratio of 1:1.1 mol/mol of ADA and DEG in benzene. At the same time, adding up to 1.5 ml of distilled water gradually increases the optical density of the system (characterizing the turbidity of the solution).  

Then the addition of a small amount of precipitant leads to a significant increase in optical density. This condition is maintained until 3.6 ml of precipitate is added. At the same time, if adding 1.5 ml of precipitate increases the optical density of the system by 0.125 D, then adding 3.6 ml of precipitate this figure reaches 1.345 D. After that, the subsequent addition of the precipitant no longer changes the optical density of the system, which means that the precipitation of the oligomer from solution is complete. The nature of the turbidimetric titration curve can be explained by the settling of molecules of the same structure, but different molecular weights.

In Figure 2, the graph shows a polyester synthesized in a ratio of 1:1.5 mol/mol between ADA and DEG.

In this case, adding up to 1.2 ml of the precipitant to the polyester leads to a gradual increase in the optical density of the system. The subsequent addition of the amount of sediment dramatically increases the optical density. This condition is maintained until 2.1 ml of precipitant is added, and the turbidity of the solution remains unchanged when the precipitant is added to 3.0 ml. At the same time, if the optical density of the system increases by 0.391 D when 1.2 ml of sediment is added, and when 2.1 ml of sediment is added, this figure reaches 1.091 D.

A detailed analysis of the state of this curve shows the partial two-component nature of this system. That is, the addition of 0.3 ml of precipitant in the range of 1.2 ml means that the first component precipitates and the second component begins to precipitate. After the addition of 3.0 ml of precipitate, the second component also completely precipitates, in which case it can be considered as a system. It is appropriate to describe the process of sequential immersion, characteristic of two components, by a broken curve.

Conclusion. Summarizing all the studied data, we can conclude that the molecular weight of polyester synthesized from ADA and DEG in the ratio of 1:1.1 mol/mol, 1:1.5 mol/mol from these known substances is higher than that obtained in the ratios . The explanation for this situation and its accuracy can be seen by the turbidimetric titration method.

It is shown that an increase in the molar content of diethyl glycol (DEG) in polyester leads to a decrease in the optical density of the system, as well as in the sedimentation time. That is, due to the presence in the system of excess DEG molecules that do not react, the mass of the substance and its optical density are small. This is also evident when observing the gradual sinking phenomenon in turbidimetry.

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