SU523109A1 - The method of obtaining the mixed cellulose esters - Google Patents

Description

congestion. For example, for the reaction of the NC and CH3SOC at 20 ° C, the dependence of the nitrogen content in the resulting product 60 minutes after the reaction has been delayed and the concentration of A1Cl3 is: In N (%) 2.501 - 0.248 A1Cl1, g 0.983. However, as evidenced by experimental data, along with the formation of acyl cellulose derivatives, oxidative transformations occur to a small extent, and the number of carboxyl groups, determined by potentiometric synthesis, monotonously increases with increasing concentration of A1Cl3 (see Table 1). Therefore, the amount of the catalyst required for the reaction in each individual case should be determined, based on considerations of expediency: the optimum is needed at which the minimum formation of a COOH group corresponds to the maximum substitution of nitro groups. Table 1 Changes in the nitrogen content and the number of carboxyl groups in the interaction of NC (N 12.4, COOH-groups 0.15%) with acetyl chloride at 60 minutes after the start of the reaction. As can be seen from the data table. 1, the reaction proceeds at a noticeable rate already at 20 ° C with a relatively high content of LCC. An increase in the temperature of the reaction mixture makes it possible to significantly increase the reaction rate 45 The influence of solvents on the rate of transfer of acylamide chloride in the presence of A anhydroglucose 25 D-E-40 40 with the same content of catalyst (see Table 2). Table 2 The effect of temperature on the reaction rate of denitration in benzoyl chloride (nitrogen content in the initial nitrocellulose is 12.7%) Moreover, increasing the temperature of the reaction leads to a decrease in the amount of AlCl3 required to achieve the same result. The study of the kinetics of the catalytic denitration reaction of NTS led to the conclusion that for various chloride acyls the process almost ends within 1 hour (with a molar ratio of A1Cl: anhydroglucose unit 3: 1), however, the optimal reaction temperature is different for different acid chlorides. At the same time, the amount of acyl chloride taken in the reaction in all cases was relative to NTS 40: 1 and was dictated by considerations of the convenience of the process, since with a smaller modulus, it is difficult to uniformly distribute the catalyst in the reaction mixture due to the formation of a highly viscous mass, especially low temperatures. The use of various organic substances as a diluent of the reaction medium (solvent NC) in some cases has a significant effect and, as a rule, causes a decrease in the rate of the transesterification reaction (see Table 3). Table 3 Indicators NTS (nitrogen content 12.7%) s (molar ratio AiCis: link 3: 1)

 Reaction time 25 min. Reaction time 85 min.

In the framework of the donor-acceptor interaction theory, the decrease in the rate of formation of acyl derivatives in the presence of solvent molecules having a free electron pair is explained by the competing process of coordinating these molecules with AIGU due to the vacuite orbitals of the central Lewis acid atom with the formation of the complex AlCl, solvent. Such coordination in the general case prevents the activation of the acid chloride and the subsequent nucleophilic substitution of the nitro group, the mechanism of which can be (Provide the following scheme:

RCOCl-f-AlCl, - (RCO-A1CU)

Zell -0-НО2 + (КСО-А1С14) Cell-O-COR + NO-iCl + AlClj.

However, the reaction of the formation of acyl cellulose derivatives can in some cases be carried out using NC as the solvent (diluent of the reaction medium) various organic solvents that do not prevent the formation of the acylating complex with the acid chlorides used in the reaction, and in this case the concentration ratio of acyl chloride and NC is at least 40: 1.

This method of producing acyl cellulose derivatives allows to obtain highly substituted esters even when using cellulose nitrate with a degree of substitution of 150. For example, using as the initial NC with a nitrogen content of 10.16%, cellulose triacetate containing 43.88% of acetyl groups is obtained, i.e. with a degree of substitution of 289.4; the residual nitrogen is 2.02% (the reaction is carried out at 40 ° C in the absence of any solvents, using an excess of acetyl chloride, modulus 1:40, threefold excess of A1Cl3). Cellulose under the same conditions gives a product with a degree of substitution of only 66.81, i.e., 15.11% of acetyl groups.

Example 1. A mixture of 0.48 g of cellulose nitrate (nitrogen content 12.40%) and 19.80 g of acetyl chloride is heated to 40 ° C, and then 1.87 g of aluminum chloride is added under stirring. The reaction is carried out within an hour. After cooling to room temperature, dry sodium bicarbonate is added to the reaction mixture until the bubbling stops. The product is planted with alcohol, washed with 1% acetic acid, water and dried at 105 ° C. Yield 0.46 g (98.70%).

The degree of substitution of the ester, determined by saponification of the resulting product with an alkaline solution for 72 hours at room temperature, followed by titration, is equal to 2.96 (or 44.65% acetyl groups). IR spectra are characterized by clear absorption maxima at, 1750, 1240 and 610 cm, characteristic of

СНЗСО-groups. Residual nitrogen 1.10%. In addition, the product contains 2.24% chlorine.

Example 2. A mixture of 0.42 g of cellulose nitrate (nitrogen content 12.40%) and 18.28 g of benzoyl chloride is heated to a temperature of 70 ° C, then 1.87 g of aluminum chloride are added with stirring. The reaction is carried out within an hour. Then the reaction mass is cooled to room temperature, the product is planted with diethyl ether, washed

0 0.1 n. HC1, water and dried at 105 ° C. Yield 0.59 g (95.61%).

The degree of ester substitution determined by sodium ethylate saponification for 16 hours at room temperature followed by

5 by titration, equal to 2.42 (or 49.07% of benzoyl groups). The absorption maxima at 1615, 1575, 1500, and 1460 cm in the IR spectra of the obtained product, the C – C bond of the aromatic ring, and the band at 1740 cm, which characterizes the carbonyl group, confirm the preparation of cellulose benzoate. The product contains 0.92% residual nitrogen and 3.90%

5 chlorine.

Example 3. A mixture of 0.50 g of cellulose nitrate (nitrogen content 12.7%) and 19.68 g of valery chloride is heated to 40 ° C, then 2 g of anhydrous aluminum chloride are added with stirring. Reaction

0 is carried out for one hour with constant stirring of the reaction mixture. The mixture is then cooled to room temperature, and dry powder of sodium bicarbonate is added in small portions to it until the release of carbon dioxide bubbles. The solution of the ester obtained is decanted in 100 ml of a mixture of methanol and 50% acetic acid (1: 1) and left to stand for 2 hours.

0 total loss of polymer. The product is washed with acetic acid, water until a negative reaction to chlorine and dried at 80 ° C in a desiccator over CaC. Yield 0.50 g (71.51%).

The degree of substitution of the ester determined

5 saponification of the ester in an alkaline environment for 85 hours at room temperature, followed by titration, is 2.61 (or 58.1% of valeryl groups). Residual nitrogen 1.27%.

0

The advantages of the proposed method are the simplicity of the process and the quick completion of the reaction. In addition, the method does not require the use of additional solvents, thereby from

5, the production sphere excludes such a toxic and explosive reagent as liquid sulfur dioxide. As a catalyst, A1C1z, which is more convenient in operation, is used;

Claims (1)

The method allows the use of low-substituted cellulose nitrates with a degree of substitution of 150 and higher, whereas in the known method only cellulose trinitrates, i.e., high-5 mixed esters, can be used as the initial method. Formula of Invention A method of producing mixed cellulose esters by treating cellulose nitrates with carboxylic acid chlorides, characterized in that, in order to intensify and simplify the process, cellulose nitrates with a nitrogen content of 10.16-12.7% are used and the treatment is carried out in the presence of aluminum chloride.