CS209247B1 - Manufacturing process of glycols polyesters and dicarboxylic acids - Google Patents

Description

(54) A method for producing polyesters of glycols and dicarboxylic acids

The invention relates to a process for the preparation of polyesters of glycols and dicarboxylic acids having a molecular weight of 600 to 8000 by the transesterification of dialkyl esters of dicarboxylic acids with glycols in the presence of a transesterification catalyst. The reaction products are mainly used as plasticizers for various polymers, in particular polyvinyl chloride, cell nitrate (axes, rubber. They are also used in cable plastics, in the production of linoleum, oil and petrol resistant piping in tractors and cars, seals for refrigerators, etc. \

Methods for producing polyesters of glycols and dicarboxylic acids are widely described in the literature:

According to USSR 149 149 217, the production of polydiethylene glycol sevacinate is carried out at a temperature of 130 to 200 ° C at atmospheric pressure in a stream of nitrogen.

Disadvantages are the long transesterification time and the high content of low molecular weight compounds in the final product.

In order to overcome these disadvantages, the production of polyesters is carried out in two stages (see W. W. Korschak, S. W. Winogradow "Rawnowesnaya Polykondensatzija", Moscow, Nakula, 1968, p. 198).

According to USSR 311 311, the temperature of the production of polydiethylene glycol etcipate in the first stage of the reaction proceeds slowly to 150-180 ° C at a pressure of 19,950 Pa and 26,600 Pa. Under these conditions, the reaction is carried out until a by-product (butyl alcohol) is formed. Thereafter, the system pressure _{t is} reduced to 195 Pa to 266 Pa and at this pressure at 180 to 190 ° C the reaction is complete. ₍

The disadvantage of the process is the ^one long duration of the first stage of the reaction, since the rate of rise in temperature is limited by the boiling range of the components of the reaction mixture at a given pressure and possible sudden ebullition, or possible sudden leakage are complete, the mixture reaction.

; In order to achieve higher temperatures, a two-stage process is used to produce the polyesters in which the first step is carried out at atmospheric pressure and the second final step is carried out under vacuum. According to Japanese Patent No. 35,797, the first step in the production of polyethylene glycoterephthalate by the transesterification of dimethyl terephthalate with ethylene glycol is carried out at a temperature of 160-220 ° C at atmospheric pressure until a quantitative or almost quantitative yield of methanol as a by-product. The second stage 00247 is carried out at a temperature of 275 to 25 ° C at a pressure of 39.9 Pa to 6.65 Pa.

The disadvantage of this process is the long duration of the first stage reaction, which is 72 hours.

The reduction of the time of the transesterification reaction is achieved by carrying out the reaction in an inert gas stream. According to U.S. Pat. No. 3,386,960, polyethylene glycol terephthalate is produced, for example, by heating the reaction mixture to a temperature of 217 ° C in a slow soul stream at atmospheric pressure. Then the pressure is reduced to 133 Pa to remove it; excess glycol, and the reaction is completed within 2 hours at 280 ° C under the indicated vacuum.

According to Japanese Patent No. 40,711, the production of polyethylene glycol terephthalate is carried out in a stream of nitrogen at a temperature of 180 to 210 ° C at atmospheric pressure. The second step is carried out by raising the temperature to 280 ° C and reducing the pressure to 13.3 Pa.

Carrying out the production of polyesters of glycols and dicarboxylic acids in an inert gas stream makes it possible to improve the conditions for the removal of the by-product (aliphatic monovalent alcohol) and some reduction in the duration of the first phase of the reaction. However, losses in the raw materials and the by-product reaction increase strongly since they are difficult to condense and collect from the inert gas stream. For example, according to Japanese Patent No. 407111, an excess of glycol more than twice the stoichiometric amount is used during the transesterification.

An industrial process for the production of polyesters of glycols and dicarboxylic acids by the transesterification of dialkyl esters of dicarboxylic acids by glycols in the presence of a transesterification catalyst is well known. The reaction is carried out at a temperature of 150 to 250 ° C at an initial pressure of P _o = 101,080 Pa to 26,600 Pa over a period of 0.5 to 3 h, then at said temperature to reduce the initial pressure P _o to 19,950 Pa to 133 Pa final pressure. P _k , after which the transesterification is completed at the same temperature and the stated final pressure P _k .

A disadvantage of the known methods is that the duration of the transesterification reaction is long and the raw material (glycol) with the by-product reaction aliphatic monovalent alcohol removed from the reaction is lost. Due to the disturbance of the composition of the reaction mixture caused by the loss of the glycol with the distilled alcohol, end products are produced whose molecular weight is 1.3 to 3 times less than calculated. In addition, in many cases the end products are of insufficient color (Fe-Cu-Co color index corresponds to No. 30). The products produced are characterized by a high acid number (e.g. 2.2 mg KOH / g).

The purpose of the present invention is to overcome these disadvantages.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for the production of polyesters of glycols and dicarboxylic acids by transesterification of dialkyl esters of dicarboxylic acid glycols while reducing the initial pressure P 0 _to the final pressure P _k .

This object is achieved by proposing a process for the preparation of polyesters and dicarboxylic acids by the transesterification of C 1 -C 6 dialkyl esters of C 1 -C 12 dicarboxylic acids of the general formula

HOCH ₂ -C (R _n R _{m) (CH2) q} -OH wherein represents

R is hydrogen, methyl, m is 0 to 2, n is 0 to 2, q is 0 to 8, or

HO (CH ₂ CH ₂ O) _x H, where x is 1-10, in the presence of a transesterification catalyst at which the reaction is carried out at a temperature of 150 to 250 ° C and an initial pressure P _of 101 080 Pa to 26 600 Pa after 0.5 to 3 hours, then at said temperature, reducing the initial pressure P 0 _to a final pressure P _{k of} 19,950 Pa to 133 Pa, after which the transesterification is carried out at the same temperature and said final pressure P _k . According to the invention, the initial pressure P 0 _is reduced to the final pressure P _k according to the relation

P = P _o - B lg (τ + 1) + C lg ² (τ + 1), where P represents the present pressure in Pa, P _{o the} initial pressure in Pa, τ represents the time from the beginning of the decrease in the initial pressure P _o in hours, B, C are empirical coefficients, with B = 466 to 2080, C = 266 to 1440.

Decreases when the initial pressure P _o faster than expected by said relationship, then leads to higher foam formation, fuming overflow of the reaction mixture. In the case of a slow decrease in the initial pressure, the reaction time is prolonged due to the slow removal of the by-product (aliphatic monovalent alcohol) from the reaction zone).

Carrying out the manufacturing process of the polyesters according to the invention allows

1. shortening the reaction time by 1.5 to twice as much as obtaining optimum conditions for removing the reaction by-product, aliphatic monovalent alcohol from the reaction zone and thereby shifting the reaction equilibrium in the desired direction,

2. reducing raw material consumption by reducing glycol losses with the by-product (aliphatic monovalent alcohol) taken from the reaction,

3. improving the quality of the end products, ie increasing their viscosity, improving color (Fe-Cu-Co color index corresponds to No. 3) and acid value (to 0.8 mg KOH / g) by reducing the residence time of the reaction mixture under conditions high temperatures.

The invention can be implemented, for example, in a device consisting of a kettle with a stirrer having a heating and cooling jacket or a heating and cooling jacket.

serpentine piping, rectification column and vapor condensation system, p

To produce the polyester into the reactor can be the starting reactants, glycol and dialkyl dikarboxylpvé acids, and transesterification catalyst, the reaction mixture was stirred and heated to 150-200 ° C, in that the pressure (P _o) in the system depending on the type of catalyst permanently maintained in the range 101 080 Pa to 26 600 Pa. After 0.5 to 3 hours of heating, the indicated initial pressure P 0 _is reduced to a final pressure P _of 19.950 Pa to 133 Pa according to the aforementioned relationship. The pressure reduction of the system in accordance with the n-proposed relationship can be accomplished by means of an automatic control consisting of a vacuum meter, a software device, a control device, a valve and a vacuum line.

After reaching the final pressure P _k , the transesterification reaction is carried out at a temperature of 150 to 200 ° C and at a constant pressure P _k until the reaction mixture reaches the hydroxyl value which is desired.

The distillable mixture of glycol vapors and the by-product reaction aliphatic monovalent alcohol resulting from the transesterification flows into a rectification column in which it is separated into glycol and alcohol. The glycol is continuously returned from the bottom of the rectification column to the reaction while the alcohol after condensation enters the column, the remainder being removed from the reaction.

Various esters of aliphatic and aromatic acids, such as adipic, sebacic, phthalic and aliphatic monohydric alcohols, for example methyl alcohol and butyl alcohol, can be used as starting dialkyl esters of dicarboxylic acids. Examples of glycols are ethylene glycol, diethylene glycol, 1,2-propylene glycol. Suitable catalysts are any of the transesterification catalysts, such as tetrabutoxytitanium, zinc acetate, n-dibutyltin dicaprylate, zinc acetate-activated carbon mixture, n-dibutyltin dicaprylate-activated carbon mixture.

In order to better understand the invention, the following are examples of specific embodiments thereof.

He did

In a periodically operating apparatus comprising a 3.2 m ³ boiler with stirrer, heating coils and cooling jacket, a 7 m high packing column, a condensation and trapping system and a distillation receiver, polypropylene glycol adipate is obtained by transesterification of dibutyl adipate with 1,2-propylene glycol in the presence of a catalytic zinc acetate-activated carbon system.

The reactor is charged with 1550 kg of dibutyl adipate, 420 kg of 1,2-propylene glycol, 15 kg of zinc acetate, 32 kg of activated carbon. After completion of the filling, steam is introduced into the coil tubes of the reactor and the reaction mixture is started to be heated at a pressure of 10 mm Hg. After 50 min, the temperature of the reaction mixture reaches 185 ° C and the reaction is then continued at this temperature. After 1.5 h from the start of heating the pressure. in the system decreases by relationship. P = P _o - B lg (τ + 1) + C lg ² (τ + 1), where P _o = 101 080 Pa, B = 2080, C = 1440.

5.5 h, the pressure P _k in the system is 2660 Pa. At this pressure, the reaction is continued for 8 hours until the hydroxyl value of the reaction mixture reaches 0.3%. The total reaction time (from the start of heating to the production of the final product) is 15 hours.

Throughout the synthesis the mixture of vapors of 1,2-propylene glycol and a by-product, butyl alcohol ^! leaving the reactor is fed to a rectification column where the mixture is separated into glycol (1,2-propylene glycol) and said alcohol; The 1,2-propylene glycol is continuously recycled from the bottom of the rectification column and the butyl alcohol after condensation partially enters the column while the remainder or reaction is withdrawn.

For comparison, the same synthesis is performed according to known technology. Synthesis was performed as described above, but proceeding at atmospheric pressure (101.080 Pa) at 185 ° C up to 80% conversion. The system pressure is then reduced to 2660 Pa over a period of 60 min and the reaction is continued at said pressure and at a temperature of 185 ° C until the reaction mixture reaches a hydroxyl value of 0.3%. The first stage (at atmospheric pressure) lasts 23 hours, the second stage (at 2660 Pa) for 6 hours.

In order to compare the quality of the polyesters obtained by the process according to the invention and in a manner known per se, samples are taken and qualitatively analyzed during both processes. The results of the analyzes are shown in Table 1.

Example 2

In the apparatus described in Example 1, polydiethylene glycol adipate is obtained by transesterification of dibutyl adipate with diethylene glycol in the presence of a catalytic zinc acetate-activated carbon system.

* 1600 kg of dibutyl adipate, 510 kg of diethylene glycol, 16 kg of zinc acetate, 32 kg of activated carbon are charged into the reactor. After completion of the filling, the system pressure was reduced to 26 Pa and the reaction mixture started to heat. After 0.5 hours of heating, the system pressure at 150 ° C was reduced according to the relationship

P = P _o - B lg (τ + 1) + C lg ² (τ + 1), where P _o = 26,600 Pa, B = 466.8, C = 226.4. After 3 hours, the system pressure was 133 Pa. The reaction is continued at a temperature of 150 ° C at the pressure indicated for 17 hours until the reaction mixture has a hydroxyl value of 0.45%. The total reaction time was 20.5 hours.

For comparison, the same synthesis is performed by technology. Synthesis is carried out as described above, only proceeding at a temperature of 150 ° C and a pressure of 26 600 Pa up to 90% conversion. Thereafter, the pressure drops to 133 Pa over 30 minutes and at this pressure and at 150 ° C the reaction is continued until the reaction mixture reaches a hydroxyl value of 0.45%. The total reaction time is 27 hours.

To compare the quality of the polyesters obtained by the method of the invention and in a manner known per se, samples are taken and qualitatively analyzed during both processes. The results of the analyzes are shown in Table 1.

Example 3

In the apparatus described in Example 1, polydiethylene glycol sebacate is obtained by transesterification of dibutyl sebacate with diethylene glycol in the presence of a catalytically active n-dibutyltin dicaprylate-activated carbon system.

1600 kg of dibutyl sebacate, 470 kg of diethylene glycol, 1.42 kg of n-dibutyltin dicrylate, 40 kg of activated carbon are charged to the reactor. After the filling was completed, the reaction mixture was started to warm at atmospheric pressure. After 1.2 h the temperature reached 200 ° C and the reaction was then carried out at this temperature. After 2 hours of heating, the system pressure is reduced according to the relationship

P = P _oi - Bg (τ + 1) + Cg ² (τ + 1), where P _o = 101 080 Pa, B = 1992, C = 1322. After 5 hours, the system pressure is 1330 Pa. At this pressure and at 200 ° C, the reaction is continued until the hydroxyl value of the reaction mixture reaches 0.3%.

In order to compare the quality of the polyesters obtained by the process according to the invention and in a known manner, samples are taken and qualitatively analyzed during both processes. The results of the analyzes are shown in Table 1.

Example 4

In the apparatus described in Example 1, polyethylene glycol phthalate is obtained by transesterification of dimethyl phthalate with ethylene glycol in the presence of tetrabutoxytitanium catalyst.

1700 kg of dimethyl phthalate, 410 kgethylene glycol and 2.21 kg of tetrabutoxytite are charged to the reactor. After the filling was complete, the system pressure was reduced to 79.800 Pa and the reaction mixture started to heat. After

The temperature was reached at 250 ° C for 1.5 h and the reaction was then carried out at this temperature. After 3 hours of heating, the system pressure is reduced according to the relationship

P = P _o - B lg (τ + 1) + C lg ² (x + 1), where P _o = 79,800 Pa, B = 1,030.2, C = 552.8. After 4 hours, the system pressure was 19,950 Pa. The reaction is continued at this pressure and at a temperature of 250 ° C until the hydroxyl value of the reaction mixture reaches 0.3%.

For comparison, the synthesis is carried out by known technology. Synthesis is carried out as described above, but only takes place at a temperature of 250 ° C and a pressure of 79 800 Pa up to 85% conversion. Thereafter, the system pressure is reduced to 200 psig over 45 minutes and the reaction is continued at the specified pressure and 250 ° C until the hydroxyl value of the reaction mixture reaches 0.3%.

In order to compare the quality of the polyesters obtained by the process according to the invention and in a manner known per se, qualitative analysis is carried out during both processes. The results of the analyzes are shown in Table 1.

Table 1

Example Hydroxyl number% Viscosity at 25 ° C, mPa. with Acid number mg KOH / g Color index according to Fe-Cu-Co scale Molecular mass way according to vyná- lezu known way way according to vyná- lezu known way way according to vyná- lezu known way way according to vyná- lezu known way way according to vyná- lezu known way 1 0.3 0.3 1 800 90 2,0 2.2 No 5, No 5 1 200 400 2 0.45 0.45 180 110 1.5 1.5 No 3 No 3 600 460 3 0.3 0.3 1 440.10 ³ J 140.10 ³ 0.8 2.1 No. 10 No 30 8 000 6 150 4 0.3 0.3 460 270 1.2 ’ 1,8 No 3 No 5 860 670

In addition to determining the quality of the end product, the total reaction time (from the start of heating to the production of the end product) was measured in each example, the amount of aliphatic monovalent alcohol withdrawn from the reaction after rectification was measured and the glycol content of said alcohol. Data is shown in Table 2.

Table 2

At- klad Total reaction time, h Glycol content of aliphatic monovalent alcohol, % wt. Aliphatic monovalent alcohol losses,% by weight way way way according to known according to known according to known vyná- way vyná- way vyná- way lezu lezu lezu 1 15 Dec 29 1.0 6.0 2,0 11.9 2 20.5 27 Mar: 2,0 3.2 3.0 12.0 3 27.0 44.5 0.5 4.0 2.1 10.0 4 19.0 29 1.1 5.4 2.8 11.5

Thus, the production of the polyesters according to the invention makes it possible to reduce the reaction time by 1.5 to 2 times, to reduce the losses of aliphatic monovalent alcohol from 10 to 12% to 2 to 3%, to produce a final product with predetermined molecular weight, better color and acid number below 2 mg KOH /G.

Claims (1)

SUBJECT Process for the preparation of polyesters of glycols and dicarboxylic acids by transesterification of C 1 -C 6 dialkyl esters of dicarboxylic acids of C 1 -C 12 glycols of the general formula HOCH ₂ C (R 1 R _m ) (CH ₂ ) _q OH where it represents R is hydrogen, methyl, m is 0 to 2, n is 0 to 2, q is 0 to 8, or ΗΟ (€ Η ₂ αΗ ₂ Ο) "Η, where x is 1 to 10, in the presence of a transesterification catalyst, at which the reaction is carried out at a temperature of 150 to 250 ° C and an initial pressure P _of 101 080 Pa to VYNALEZU 26 600 Pa for 0.5 to 3 hours, then, at said temperature, the initial pressure P _{o is} reduced to a final pressure P _{k of} 19 950 Pa to 133 Pa, after which the transesterification is carried out at the same temperature and pressure P _k , that is, the initial pressure P _{o is} reduced to the final pressure P _k according to the equation ¹ I P = P _o - B lg (τ + 1) + C lg ² (τ + 1), where P represents the present pressure in Pa, P _{o the} initial pressure in Pa, τ from the beginning of the decrease in the initial pressure P _o in hours, B, C are empirical coefficients, with B = 466 to 2080 and C = 226 to 1440.