CS209248B1 - Manufacturing process of glycols polyesters and dicarboxylic acids - Google Patents

Description

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

The present 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. The reaction products serve mainly as plasticizers for various polymers, in particular for polyvinyl chloride, cellulose nitrate, rubber. They are also used in cable plastics, in the production of linoleum, oil and petrol resistant pipelines in tractors and cars, seals for refrigerators, etc.

It is known to produce polyethylene glycol terephthalate by transesterification of dimethyl terephthalate with ethylene glycol at a temperature of 150 to 200 ° C at a pressure of 101 325 Pa to 665 Pa. To accelerate the transesterification process, one of the starting materials, namely ethylene glycol, is dewatered before the transesterification. The dewatering of the ethylene glycol is carried out in a separate apparatus by heating under vacuum at 120-160 ° C with distillation of the glycol-water mixture. 2 to 20% of ethylene glycol is lost during dewatering (see GDR Patent No. 73,652).

The known method of producing polyesters has significant disadvantages:

1. Conducting dewatering as a separate stage y in a separate apparatus results in the process being complicated as a whole, additional equipment is required and the total process time is extended by 5 to 10%.

2. Only one of the reactants, glycol, is subjected to dewatering, although commercial dialkyl dicarboxylic acid esters, as shown by the tests, contain 0.05-0.30% water. Due to the use of undried diester, the transesterification catalyst is partially hydrolyzed, especially when using a diester soluble catalyst (e.g., n-dibutyltin dicrylate), and the process is prolonged by 1.8 to 2 times.

3. During dewatering, 2 to 20% of the glycols are lost by distillation as a glycol-water mixture.

The purpose of the invention is to overcome the aforementioned disadvantages.

SUMMARY OF THE INVENTION The present invention aims to change the dewatering conditions of the starting materials in order to reduce feedstock consumption standards in a process for producing polyesters of glycols and dicarboxylic acids by transesterification of dialkyl esters of dicarboxylic acid glycols.

This object is achieved by proposing a process for the preparation of polyesters of glycols and dicarboxylic acids by the transesterification of C 1 -C 6 dialkyl esters of C 2 -C 12 dicarboxylic acids of the general formula

HOCH ₂ C (R _n R _m ) (CH ₂ ) _q OH, wherein 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 to 10, in a transesterification reactor at a temperature of 150 to 250 ° C and a pressure of 101 325 Pa to 665 Pa under dewatering by distillation of the starting reaction mixture. According to the invention, the dewatering of the starting reaction mixture is carried out before the transesterification in the same reactor as the transesterification by adding to the starting reaction azeotropic mixture component in an amount of 3 to 15%, preferably 5 to 10%; based on the weight of the starting reaction mixture. Thereafter, the azeotropic mixture is distilled off at a temperature of 50-100 ° C and at a pressure of 10-120 mbar.

Aliphatic monovalent alcohols having 2 to 4 carbon atoms are used as the water-forming component of the azeotropic mixture. .

The experimentally determined amount of azeotropic mixture with water of 3 to 15% ensures optimal conditions for carrying out the reaction. When less than 3% is used, first the partial entrainment of the glycol by the distilled azeotropic mixture occurs and, secondly, the dewatering of the reactants ends at a higher temperature, causing hydrolysis of the transesterification catalyst. The use of more than 15% increases the consumption of heat and coolant, reducing the effective volume of the reaction equipment by not giving a technological effect.

Any compound which forms an azeotropic mixture with water can be used as the dewatering component. They are preferably aliphatic monovalent alcohols having 2 to 4 carbon atoms corresponding to the starting diesters. The azeotropic mixture distillable from the reactants during dewatering and the by-product carried during synthesis, the aliphatic monovalent alcohol belonging to the corresponding starting diester, can in this case be fed to the same equipment and reused without additional purification.

The process for producing the polyesters according to the invention has these advantages;

1. Conducting dewatering and re-esterification in the same reactor allows simplification of the instrumentation of the process, the reaction time is reduced by 5 to 10%, the energy requirement is reduced, since dewatering takes place during the reactor start-up time, i.e. during the reactor melting.

2. Hydrolysis of the catalyst is prevented, thereby reducing its activity, which also allows a 1.8 to 2-fold reduction in process time.

3. Drainage does not distil ξ of the glycol-water mixture, which can reduce glycol consumption standards by 2 to 20%.

4. The use of an aliphatic monovalent alcohol belonging to the starting dialkyl dicarboxylic acid esters as a water-forming component of the azeotropic mixture allows a reduction in consumption standards; alcohol by 2 to 4% by eliminating alcohol purification.

The apparatus for carrying out the process according to the invention consists of a periodically or continuously operating reactor and a vapor separation system flowing from the reactor. Any esterification apparatus such as a boiler, a multi-piece apparatus, a cascade can serve as the reactor; da z‘reaktorů. The separation system may be provided; for example as a rectification column (packed column on a qebo tray column) in conjunction with a reactor.

To produce the polyester, a dicarboxylic acid dialkyl ester, a glycol, a transesterification to the catalyst and a water-forming azeotrope component are added to the reactor. Thereafter, the reactants are heated to a temperature of 150 to 250 ° C at a pressure of 10 mm Hg. ^; During heating, the reactants are dewatered by distilling water and the water-forming components of the azeotrope. The dewatering of the network ends at a temperature not exceeding 100 ° C. When the temperature of the reaction mixture reaches 150-250 ° C, the heating is terminated and the transesterification is carried out at the indicated temperature at a pressure of 10 mm Hg

665 Pa of residual pressure.

_t vaporized mixture of glycol and an aliphatic monohydric alcohol formed during the transesterification is divided into s column in rektifikaéní glycol and alcohol. In a column boiler, the glycol is continuously fed back into the process. The alcohol vapors are condensed in a cooling condenser, some of the condensate is sprayed onto the column while the remaining alcohol is withdrawn from the process.

Various esters of aliphatic and aromatic acids, such as phthalic, adipic, sebacic and aliphatic monohydric alcohols, such as methanol and butyl alcohol, can be used as starting dialkyl esters of dicarboxylic acids.

Suitable glycols are, for example, ethylene glycol, diethylene glycol and 1,2-propylene glycol.

The catalysts can be any of the transesterification catalysts, for example, tetrabutoxytitanium, zinc acetate, n-dibutyltin dicaprylate, activated carbon, a mixture of zinc acetate and activated carbon, a mixture of n-dibutyltin dicaprylate and activated carbon.

As the water-forming components of the azeotropic mixture, for example, aliphatic monovalent alcohols having 2 to 4 carbon atoms, benzene, toluene, 1,4-dioxane can be used.

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

He did

In a periodically operating apparatus comprising a 10 liter stirrer with stirrer, heating and cooling jacket, and packed column, polydiethylene glycoladipate is obtained by transesterification of dibutyl adipate with diethylene glycol in a catalyst having a n-dibutyltin dicaprylate activated carbon system. The n-butyl alcohol serves as the water-forming component of the azeotropic mixture.

The reactor was charged with 5800 g of dibutyl adipate, 2400 g of diethylene glycol, 1230 g (15% based on the weight of the starting reactants) of n-butyl alcohol, 5.15 g of n-dibutyltin dicrylate and 145 g of activated carbon. The system pressure was then reduced to 5 mm Hg and the reaction mixture was heated to 250 ° C. The reaction mixture is dewatered during heating. The mixture of n-butyl alcohol and water vapor produced during the dewatering process is removed from the process. When the temperature of the reaction mixture reached 95 ° C, the distillation of the glycol-water mixture was terminated. Diethylene glycol was not detected in the distillate.

After reaching the reaction temperature of 250 ° C, the pressure is reduced to 3325 Pa and the esterification is carried out under these conditions and the reaction is terminated after 270 minutes of heating of the reaction mixture when the reaction mixture has a hydroxyl number of 0.3%.

For comparison, the same synthesis is carried out in the described apparatus by known technology. First, the dehylene glycol is dewatered in a separate apparatus. To this end, 2560 g of diethylene glycol are introduced into the apparatus and dewatered by distilling the glycol-water mixture at 150 [deg.] C. at a pressure of 1330 Pa. 160 g of diethylene glycol (6.25% by weight of the starting mixture) were distilled off with the glycol-water mixture. The process takes 60 min. After the de-watering of the diethylene glycol is cured, it is transferred to a transesterification reactor. The same reactor was charged with 5800 g of dibutyl adipate, 5.15 g of n-dibutyltin dicrylate and 145 g of activated carbon, and the reaction was carried out at 250 ° C and 3325 Pa. Where the hydroxyl value of the reaction mixture reached 0.3% was 300 min and the total process time 480 min. /

In order to compare 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 are summarized in the table. ^!

Table

Quality values Way according to invention Known way Color index by scale Fe-Cu-Co c No. 4 Hydroxyl number,% 0.3 0.3 Viscosity at 25 ° C, mPa. with 30 000 26 500 Molecular weight 8 000 7 600 Acid number, mg KOH / g 2.5 3.2

Example 2

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. 1,4-dioxane is used as the water-forming component of the azeotropic mixture. ^;

6200 g of dimethyl phthalate, 2300 g of ethylene glycol, 8.05 g of tetrabutoxytitanium and 850 g of 1,4-dioxane (10% based on the weight of the starting reaction mixture) are introduced into the reactor. After the filling was complete, the system was depressurized to 2660 Pa and the reaction mixture was heated to 150 ° C. The distillation of the azeotropic water-1,4-dioxane mixture was terminated at 30 ° C. Ethylene glycol was not detected in the distillate.

After reaching the reactor temperature of 150 ° C, the pressure is reduced to 1330 Pa and the transesterification is carried out under the specified conditions. The reaction is complete after 360 minutes of heating the reaction mixture when the hydroxyl value of the reaction mixture reaches 0.3%.

A polyester is obtained with the following values: c.

i. on a Fe-Cu-Co # 3 scale, molecular weight 1000, viscosity at 25 ° C 250 mPa. s, acid number 1.5 mg KOH / g.

Treasure of 3 h In the apparatus described in Example 1, polyethylene glycol adipate is obtained by transesterification of dibutyl adipate with diethylene glycol in the presence of a catalytically acting zinc acetate-active gravity system. Benzene is used as the water-forming component of the azeotropic mixture.

5800 g of dibutyl adipate, 1880 g of diethylene glycol, 21 g of zinc acetate, 42 g of activated carbon and 390 g of benzene (5% by weight of the starting reaction mixture) are introduced into the reactor. After the filling was complete, the system pressure was reduced to 66.5 mbar and the reaction mixture was heated to 190 ° C. Distillation of the azeotropic benzene-water mixture was terminated at 70 ° C, diethylene glycol was not detected in the distillate.

¹ When the reaction temperature is 190 ° C, the pressure is reduced. to 665 Pa, and under the conditions indicated, a transesterification is carried out. The process is completed after 210 minutes of heating the reaction mixture when the hydroxyl number ^{1 of the} reaction mixture reaches 0.3%.

A polyester is obtained with the following values: c. according to Fe-Cu-Co scale No. 2, molecular weight 1500, viscosity at 25 ° C 350 mPa. s, acid number 2 mg KOH / g.

Example 4

In the apparatus described in Example 1, polypropylene glycol sebacate is obtained by transesterification of dibutyl sebacate with 1,2-propylene glycol in the presence of zinc acetate catalyst. As a folder? forming an azeotropic mixture with water serves n-butyl alcohol.

6200 g of dibutyl sebacate, 1150 g of 1,2-propylene glycol, 19.5 g of zinc acetate, 220 g of n-butyl alcohol (3% based on the weight of the starting reaction mixture) are introduced into the reactor. After the filling was complete, the reaction mixture was started to warm at atmospheric pressure. The distillation of the water-n-butyl alcohol mixture was terminated at 100 ° C. 1,2-Propylene glycol was not detected in the distillate.

After reaching the reactor temperature of 200 ° C, the heating of the reaction mixture was stopped and the transesterification was carried out at the indicated temperature and atmospheric pressure. The process was terminated after 370 minutes of heating the reaction mixture when the hydroxyl value reached 0.35%.

A polyester is obtained with the following values: c.

1. On a Fe-Cu-Co scale No. 3, molecular weight 600, viscosity at 25 ° C 150 mPa). s, acid number 2.5 mg KOH / g.

Example 5

In the apparatus described in Example 1, polypropylene glycol adipate is obtained by transesterification of dibutyl adipate with 1,2-propylene glycol in the presence of a catalytically active system of n-dibutyltin dicrylate activated carbon. Toluene serves as the water-forming component of the azeotropic mixture.

6000 g of dibutyl adipate are introduced into the reactor,

Claims (2)

SUBJECT AND Process for the preparation of polyesters of glycols and dicarboxylic acids by the transesterification of C 1 -C 6 dialkyl esters of C 2 -C 12 dicarboxylic acids of the general formula HOCH ₂ C (R _n R _m ) (CH ₂ ) _q OH, where 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 to 10, in a transesterification reactor at a temperature of 150 to 250 ° C and a pressure of 101 325 Pa to 665 Pa under a 1520 g 1,2-propylene glycol drainage, 5.5 g n -dibutyltin dicaprylate, 155 g of activated carbon and 540 g of toluene (7% based on the weight of the starting reaction mixture). After completion of the filling, the pressure is reduced to 79.8 mm Hg and the reaction mixture is heated to 210 ° C. The distillation of the toluene-water mixture was completed at 82 ° C. 1,2-Propylene glycol was not detected in the distillate. After reaching a reaction temperature of 210 ° C, the pressure is reduced to 3325 Pa and the transesterification is carried out under the indicated conditions. The reaction is terminated after 320 minutes of heating the reaction mixture when the hydroxyl value reaches 0.3%. A polyester with the following values is obtained: ci) on the Fe-Cu-Co # 3 scale, molecular weight 2550, viscosity at 25 ° C 1200 mPa. s, acid number 1.8 mg KOH / g. BACKGROUND OF THE INVENTION The distillation of the starting reaction mixture is characterized in that the dewatering of the starting reaction mixture is carried out before the transesterification in the same reactor, wherein azeotropic mixture component is added to the starting reaction mixture in an amount of 3 to 15%, preferably 5 to 10%. based on the weight of the starting reaction mixture, and then the azeotropic mixture is distilled off at a temperature of 50 to 100 ° C and at a pressure of 10 mm Hg to 2660 Pa. 12. Process according to claim 1, characterized in that aliphatic monovalent alcohols having 2 to 4 carbon atoms are used as the water-forming component of the azeotropic mixture.