JPS5952894B2 - Manufacturing method of polyester of glycol and dicarboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention achieves a molecular weight of 60 by transesterifying a dialkyl ester of a dicarboxylic acid with a glycol.
0 to 8,000 polyester of glycol and dicarboxylic acid.

The reaction products are primarily used as plasticizers for various polymers, including polyvinyl chloride, nitrocellulose, and rubber. In addition, the reaction product is made into cable plastic.
Used for manufacturing linoleum, oil- and gasoline-resistant fuel pipes for tractors and automobiles, gaskets for refrigerator cabinets, etc. Processes for producing polyesters of glycols and dicarboxylic acids are known in the art (USSR Inventor Certificate Haruka 311950, Cl, c08g63/16;
B, V, Petuknov “PolyesterFib
res'', MoscowGoskhimi2datP
ublisning House, 1960, pp. 1
9-22, 41-44). According to these prior art methods, the reagents, dialkyl esters of dicarboxylic acids and glycols, are charged to the reactor in stoichiometric ratios and in excess of glycol. If the process is carried out in the presence of a transesterification catalyst, catalysts such as zinc acetate and activated carbon are additionally charged to the reactor. The reaction mixture is heated to a temperature of 100-300 °C, depending on the individual properties of the products and catalyst, and the reactor pressure is between 1 atm (absolute) and a residual pressure of 5 mm Hg.
maintained within the range. Transesterification is a reversible reaction;
Therefore, in order to shift the equilibrium to the right, reaction by-products, namely aliphatic monohydric alcohols, are continuously distilled off from the reactor. It is inevitable that glycol is distilled off together with this alcohol. To this end, the distillate product is subjected to separation to separate alcohol and glycol, the alcohol being withdrawn from the process while the glycol is recycled to the process. The separation is carried out in a rectification column equipped with packing and attached to the top cover of the reactor. The filling part of the reactor is Raschigrings.
is packed, and a condenser-cooler is provided at the top of the column. The aliphatic monohydric alcohol vapor moves upwards and is condensed in the condenser-cooler. From the condenser-cooler, a portion of the condensed alcohol is fed as reflux to the column spray;
The remainder of the alcohol is removed from the system. Glycol is continuously discharged from the lower part of the column and recycled to the process. The separation efficiency of the column is controlled by the steam temperature at the column outlet and adjusted by changing the reflux ratio. Therefore,
When producing polyethylene terephthalate by one of the prior art methods, the reaction by-product is methanol and the upper part of the rectification packed column is maintained at a temperature of 65-70C. The above-mentioned polyester manufacturing process of the prior art has the following essential drawbacks: (1) The composition and amount of vapors distilled off during transesterification vary substantially as the process progresses.

At the beginning of the process, the steam contains up to 90% glycol, and at the end of the process, the steam contains up to 90% aliphatic monohydric alcohol. Prior art separation methods are effective only within narrow ranges of variation in the composition and amount of the mixture undergoing separation. Therefore, as can be seen in Example 1 below, the separation method described above does not guarantee complete separation over the entire time of the process. 2 In the aliphatic monohydric alcohol distilled off (after the rectification packed column), 4-6% of glycol is present.

The loss of glycol has increased ratingcoeffic with respect to misadjustment of starting materials and reaction mass composition.
ients) coefficients. This often makes it impossible to obtain commercially acceptable products. 3 The glycol recycled to the reaction zone contains 15-20% aliphatic monohydric alcohol.

The entry of alcohol into the reaction zone slows down the transesterification process and increases its process time. 4 Increased process time can result in impaired color value of the desired product (iron-copper-
A2) by cobalt scale and up to 1 of the product
Resulting in an increased acid number of 0 mgK0H/g.

5 Inaccurate composition of the reaction mass due to loss of glycol lost with distilled aliphatic monohydric alcohol may result in 1 of the calculated value
/1.5-1/3, thus resulting in a product with reduced viscosity and density values.

The object of the present invention is to provide such a process for producing polyesters of glycols and dicarboxylic acids, which allows reducing the process time, lowering the evaluation factor with respect to the starting materials and improving the quality of the final product. be.

This and other object of the invention is to transesterify dialkyl esters of dicarboxylic acids with glycols in the presence of a catalyst at a temperature of 100-300°C and 1 atm (absolute pressure).
Transesterification is carried out at a pressure of ~5 mmHg residual pressure, the mixture of glycol and aliphatic monohydric alcohol generated during the reaction process is continuously distilled off, the above compound is separated by rectification, and the aliphatic monohydric alcohol is separated. In a method for producing a polyester of glycol and dicarboxylic acid while separating the glycol from the process and returning the glycol to the process, the separation by rectification of the mixture of glycol and aliphatic monohydric alcohol is carried out in two stages, and in the first stage Forming a mixture containing 60-95%, preferably 80-90% glycol of aliphatic monohydric alcohol and glycol and aliphatic monohydric alcohol; This is achieved by providing a method as described above, characterized in that the glycol is separated into a mixture containing 2 to 40% glycol, preferably 5 to 10%, and said mixture is recycled to the first stage of separation. Ru.

Separating aliphatic monohydric alcohols and glycols in this manner allows substantially pure alcohol to be extracted from the system during the entire transesterification process and reduces the alcohol content of the glycol recycled to the process by 3. -5%
It was found that it was possible to reduce the

It has also been found that the process according to the invention can be further improved if the second stage of separation is carried out when the glycol is heated to a temperature of up to 20° C. below its boiling point or the boiling point of the glycol.

In this way, the alcohol content in glycol is 0.
As a result, the process time can be further reduced. The process for producing polyesters of glycols and dicarboxylic acids according to the invention therefore has the following advantages: 1. Aliphatic monohydric alcohols can be completely separated from glycols during the entire process (see below) (See Example 1).

2 There is virtually no glycol present in the distillate alcohol, which makes it possible to reduce glycol losses by 6 to 12% and thus to reduce the consumption rating factor with respect to the starting material.

Under the conditions of the prior art process, the amount of glycol lost with the distillate alcohol is as high as 25%. In the glycol recycled to the 3 step, the 7 alcohol content can be reduced to 5-0%.

In this way, the alcohol concentration in the reaction mass is reduced and the reaction time is also reduced by 1/1.2-1/2 (Example 1
reference). 4 This reduced reaction time (1/1.2-1
/2) Improve the color properties of the desired product by preventing θ and glycol loss.
and a predetermined molecular weight (600 to 8
,000) and the desired products with acid values of up to 3 mg KOH/g can be obtained.

5 The apparatus with which the process of the invention can be carried out consists of a reactor of continuous or discontinuous operation and a device for separating the mixture of glycol and aliphatic monohydric alcohol.

In the discontinuous embodiment of the transesterification process, the composition and amount of the dalichol-alcohol mixture vary during the synthesis, whereas in the continuous embodiment of the process these parameters remain constant. As reactors for carrying out the process according to the invention, any esterification equipment can be used, for example distillation equipment, sectioning equipment (Sec.
tiOned) apparatus or cascade reactors can be used.

The separation device can be embodied, for example, as a two-series connected rectification column. The spray conditions in the first column (first stage of separation) are such that pure alcohol flows out from the top;
On the other hand, it is selected such that a mixture of glycol and alcohol with a glycol content of 60 to 95%, preferably 80 to 90%, is discharged from the distillation vessel of the column. The pure alcohol distilled off in the first rectification column is withdrawn from the process, and the mixture of glycol and alcohol with a glycol content of 60-95% is sent to the second rectification column (second stage of separation).

The operating conditions in the second column are chosen such that pure glycol is withdrawn from the still and a vapor mixture of alcohol and glycol with a glycol content of 2 to 40%, preferably 5 to 10%, is distilled off from the top. It will be done. The pure glycol is recycled to the transesterification step, while the alcohol glycol mixture with a glycol content of 2 to 40% is fed to the first rectification column. As already mentioned above, the separation in the second rectifying column is expedient when the glycol in the still column of the column is heated to its boiling point or to a temperature of up to 20 DEG C. below the glycol boiling point.

This allows the alcohol content in the glycol recycled to the transesterification process to be reduced to 0.5-0%, thereby reducing the overall process duration. The separation step can be carried out in a single rectification column with the vapor mixture of aliphatic monohydric alcohol and glycol introduced at the midpoint of the column. The location of the entry point depends on the nature of the alcohol and glycol and the operating conditions of the column. The vapor entry point is such that it separates the rectification column into two zones, the first (upper) zone operated under the conditions of the first separation stage and the second (lower) zone operated under the conditions of the second separation stage. Experimentally chosen to partition into bands. In the first separation stage (upper zone of the column), the starting vapor mixture is divided into alcohol which is withdrawn from the top of the column and a mixture of glycol and alcohol containing 60-95%, preferably 80-90% glycol. . This mixture, which is in the liquid phase, is continuously fed to the second separation stage (lower zone of the column) and flows down the column. In the second stage, the mixture is separated into a mixture of alcohol and glycol with a glycol and glycol content of 2 to 40%, preferably 5 to 10%. Glycol is continuously discharged from the column still and recycled to the transesterification process. A mixture of alcohol and glycol with a glycol content of 2 to 40% in the vapor phase is fed continuously to the first separation stage (upper zone of the column). It has been experimentally found that the entry point at which the above vapor mixture of alcohol and glycol is introduced into the column divides the column along its height into an upper zone and a lower zone in a ratio of 2:1 to 5:1, respectively. Ta. In the separation of glycol-alcohol mixtures in a single rectifying column, it is expedient to heat the glycol in the still column of the column to its boiling point or to a temperature of up to 20 DEG C. below the glycol boiling point.

Among the rectification columns, it is most advantageous to use packed columns or multi-stage columns with heating temperatures.

In the process according to the invention, various esters of acids belonging to the aliphatic and aromatic series, such as adipic acid, sebacic acid, phthalic acid, and aliphatic monohydric alcohols, such as methyl alcohol, butyl alcohol, are used as starting dialkyl esters of dicarboxylic acids. It can be used. Among the glycols, for example, ethylene glycol, diethylene glycol, propylene glycol-1,2 can be used. As a catalyst, any conventional transesterification catalyst such as tetrabutoxytitanium, zinc acetate,
It is possible to use n-dibutyltin dicaprylate, activated carbon, a mixture of zinc acetate and activated carbon, a mixture of n-dibutyltin dicaprylate and activated carbon. For a better understanding of the invention, specific examples are described below.

Example 1 In an intermittent operation plant consisting of a 1 capacity old distillation apparatus with a stirrer, a separation apparatus consisting of a heating and cooling mantle and two rectification columns, dibutyl adipate was prepared with propylene glycol-4,2 by zinc acetate and activated carbon. Polypropylene J glycol adipate is prepared by transesterification in the presence of a catalyst system consisting of:

In the reactor, 6,200 g of dibutyl adipate, 1,5
Prepare 00g of propylene glycol-1,2, 21g of zinc acetate, and 42g of activated carbon.

The process is carried out at a temperature of 200° C. and a residual pressure of 200 mmHg. The vapors of butyl alcohol and propylene glycol 1,2 released by boiling during the synthesis were collected in a container with dimensions of 8 x 8 x 2 m.
Diameter 50mm filled with m ceramic lacquer ring
and a height of 1,000 mm and a heat exchange surface area of 0.
It is sent to a first separation stage carried out in a rectification packed column equipped with a 5 m2 cold condenser, a 0.51 m distillation pot and a 21 m distillate receiver. The vapor mixture is taken off at the top of the column, condensed in a cold condenser and mixed with butyl alcohol, which is collected in a distillate receiver, and propylene glycol l-1,2, which is fed from the still of the column to the second separation stage. Separated into a mixture of butyl alcohol. The top of the column was maintained at 84°C;
The still temperature of the column is maintained at 135°C. Propylene glycol-1 and 2 are not detected in the distilled alcohol. propylene in the mixture fed to the second separation stage.
The content of lene glycol-1,2 is 80%. 8×
In the second separation stage, carried out in a rectification packed column with a diameter of 50 mm and a height of 500 mm, filled with ceramic Krasschig rings with dimensions of 8 x 2 mm, and equipped with a 0.51 distillation pot, the first separation The mixture fed from the stage is
The propylene glycol 1,2 flows from the still column of the column into the reactor via a water seal and is separated into a mixture of butyl alcohol and glycol which is withdrawn from the top of the column and fed to the first separation stage.

The temperature at the top of the column is maintained at 110°C, and the temperature in the still column of the column is maintained at 145°C. The butyl alcohol content in the propylene glycol 1,2 recycled to the reactor is 5
%, and the content of propylene glycol-1,2 in the mixture fed to the first separation stage is 20%. The transesterification process is stopped when the hydroxyl value of the reaction mass reaches 0.3%. The reaction time is 360 minutes. For comparative purposes, similar syntheses are performed by prior art methods.

In this case, the separation of the vapor mixture of propylene glycol 1,2 and butyl alcohol takes place in a rectifying packed column installed at the reactor cover. The tower has a diameter of 50 mm and a height of 1
, 500 mm, filled with a Luschig ring of dimensions 8x8x2 mm, and provided with a cooling condenser with a heat exchange surface area of 0.5 m2 and 21 distillate receivers. The above vapor mixture of propylene glycol-1,2 and butyl alcohol is fed to the bottom of the column. Butanol vapor rises and is condensed in a cooling condenser. A portion of the condensed alcohol from the condenser is fed as reflux to the column spray to maintain the overhead temperature at 84° C., and the remaining portion of the alcohol is withdrawn from the system. Propylene glycol-1,2 is continuously discharged from the bottom of the column and recycled to the process. In this case, 0.
The time required to achieve a hydroxyl value of 3% is 48
It is 0 minutes. The content of propylene glycol-1,2 in the distilled off butyl alcohol is 6%. The butyl alcohol content in the recycled propylene glycol-1,2 is 20%. In order to compare the quality of the esters prepared by the prior art method and the method of the present invention, samples of the product were taken and subjected to qualitative analysis.

The results obtained from this analysis are shown in the table below. -;Y Example 2 Using the plant described in Example 1, polypropylene glycol adipetate is produced by transesterifying dibutyl adipate with propylene glycol-1,2 in the presence of a catalyst system consisting of zinc acetate and activated carbon. do.

6,200 g dibutyl adipate, 1,500 g propylene glycol-1,2, 21 g zinc acetate, 42
Charge g of activated carbon into the reactor.

The process is carried out at a temperature of 200° C. and a residual pressure of 200 mmHg. Propylene glycol from the reactor - 1, 2 o;
Example 1 Separation of a vapor mixture of and butyl alcohol effluent
This is done by the method described in . The butyl alcohol distilled off in the first separation stage contains propylene glycol-1,2
is not detected. The propylene glycol-1,2 content in the mixture fed to the second separation stage is 85%. The top temperature of the first rectification column is maintained at 84°C, and the temperature of the still column of the column is maintained at 138°C. In the second separation stage, the mixture fed from the first stage is mixed with propylene glycol-1,2, which flows into the reactor via a water seal, and butyl alcohol and propylene glycol-1,2, which are fed from the top of the column to the first separation stage. It is separated into two mixtures.

In the second separation stage, propylene glycol 1,2 is separated from the distillation vessel of the rectification column at its boiling point (149°C under 200mmHg pressure).
), in which case the temperature at the top of the column is 12
Maintained at 0°C. No butyl alcohol is detected in the propylene glycol-1,2 fed to the reactor. The propylene glycol-1,2 content in the mixture fed to the first separation step is 40%. The transesterification process is stopped when the hydroxyl value of the reaction mass reaches 0.3%.

The reaction time is 240 minutes. The polyester thus produced has the following properties: color A2.5 according to the iron-copper-cobalt scale; molecular weight -1,5
00; 25°C viscosity -800cp; acid number -2.35mgK
0H/G.

Example 3 Using the plant described in Example 1, polyethylene glycol sebacate is prepared by transesterifying dibutyl sebacate with diethylene glycol in the presence of a catalyst system of n-dibutyltin dicaprylate and activated carbon.

Charge the reactor with 6,200 g dibutyl sebacate, 1,800 g diethylene glycol, 4.95 g (7) n-dibutyltin dicaprylate, and 135 g activated carbon.

The process is carried out at a temperature of 200° C. and a residual pressure of 5 mmHg. Diethylene glycol and Pta from the reactor. Separation of the vapor mixture of the nol effluent is carried out according to the method described in Example 1.

Diethylene glycol is not detected in the butyl alcohol distilled off in the first separation step. Diethylene glycol content in the mixture fed to the second separation stage is 60%
It is. first. The temperature at the top of the rectification column was maintained at 20°C.
The distillation pot temperature is 78°C. In the second separation stage, the mixture fed from the first stage is separated into diethylene glycol and a mixture of butyl alcohol and diethylene glycol.

Separation is carried out by separating diethylene glycol in the distillation vessel of the rectification column at 100°C, which is 20°C lower than its boiling point (120°C/5 mmHg).
The temperature at the top of the column was 45°C.
maintained at ℃. The butyl alcohol content in the diethylene glycol fed to the reactor is 0.5%. The diethylene glycol content in the mixture fed to the first separation stage is 20%. The transesterification step is stopped when the hydroxyl value of the reaction mass reaches 0.3%. The reaction time is 280 minutes. The resulting polyester has the following properties: color A2 on the iron-copper-cobalt scale; molecular weight -2,000; viscosity at 25°C -1,500c.
P; acid number 2.55 mg KOH/GO Example 4 Using the plant described in Example 1, polyethylene glycol phthalate is obtained by transesterification of dimethyl phthalate with ethylene glycol in the presence of a tetrabutoxytitanium catalyst.

Charge the reactor with 6,200 g of dimethyl phthalate, 2,300 g of ethylene glycol, and 8.05 g of tetrabutoxytitanium.

The process is carried out at a temperature of 300° C. and a pressure of 1 atmosphere (absolute). Separation of the vapor mixture of ethylene glycol and methyl alcohol effluent from the reactor is carried out in a similar manner to Example 1.

The temperature at the top of the first rectification column is maintained at 68°C, and the temperature in the still column of the column is 135°C. The top of the second rectifying column has a temperature of 120°C, and the still temperature of this second rectifying column is 142°C. The ethylene glycol content in the methanol distilled off in the first separation stage is 0.05%.

The ethylene glycol content in the mixture fed to the second stage is 95%. The methyl alcohol content in the ethylene glycol recycled to the reactor is 3%. The ethylene glycol content in the mixture fed to the first separation stage is 2%. The transesterification process is stopped after 360 minutes.

The resulting polyester has the following properties: color A3 due to iron-copper-cobalt scale; molecular weight -600; 25
DEG C. Viscosity -180 cP0 Example 5 Using the plant described in Example 1, polypropylene glycol sebacate is prepared by transesterification of dibutyl sebacate with propylene glycol-1,2 in the presence of a zinc acetate catalyst.

Charge a reactor with 6,200 g of dibutyl sebacate, 1,150 g of propylene glycol-1,2, and 19.5 g of zinc acetate.

The process is carried out at a temperature of 100° C. and a residual pressure of 5 mmHg.
Separation of the vapor mixture of propylene glycol-1,2 and butyl alcohol effluent from the reactor. is carried out in the same manner as in Example 1.

In the butyl alcohol distilled off in the first separation stage,
Propylene glycol-1 and 2 were not detected. The propylene glycol-1,2 content in the mixture fed to the second separation stage is 75%. The temperature l at the top of the second rectifying column is 20°C, and the temperature in the distillation pot is 48°C. In the second separation stage, the mixture fed from the first separation stage is separated into propylene glycol and a mixture of butyl alcohol and propylene dalicol-1,2.

Separation is carried out by propylene glycol in the distillation tank of the rectification column.
, 2 is heated to 59°C, which is 10°C lower than its boiling point (69°C at 5 mmHg). At this time, the tower top temperature was 3
Maintained at 4°C. The butyl alcohol content in the propylene glycol-1,2 fed to the reactor is 0.5%. The propylene glycol-1,2 content in the mixture fed to the first separation stage is 35%. The transesterification process is stopped after 400 minutes.

The polyester produced has the following properties: color A2.5 according to the iron-copper-cobalt scale; molecular weight -600;
Viscosity at 5°C -150 cP0 Example 6 In a discontinuously working plant consisting of a capacity 1 old distillation apparatus equipped with a stirrer, a cooling-heating mantle and one rectification column, dibutyl adipate was distilled with diethylene glycol.
- Producing polyethylene glycol adipate by transesterification in the presence of a dibutyltin dicapryto activated carbon catalyst system.

Charge a reactor with 5,800 g of dibutyl adipate, 2,400 g of diethylene glycol, 5.15 g (7) n-dibutyltin dicaprylate, and 145 g of activated carbon.

Claims (1)

[Claims] 1 Transesterification of a dialkyl ester of a dicarboxylic acid with a glycol in the presence of a transesterification catalyst at a temperature of 100 to 300°C and a pressure of 1 atm (absolute pressure) to a residual pressure of 5 mmHg, during the reaction process. The mixture of glycol and aliphatic monohydric alcohol generated in the process is continuously distilled off, the above compounds are separated by rectification, the aliphatic monohydric alcohol is extracted from the process, and the glycol and dicarboxylic acid are removed while the glycol is returned to the process. In the method for producing polyester, the separation by rectification of the mixture of the glycol and the aliphatic monohydric alcohol is carried out in two stages, and in the first step, the aliphatic monohydric alcohol and the glycol of the glycol and the aliphatic monohydric alcohol are separated. forming a mixture containing 60-95% of glycol, separating said mixture in a second stage into a glycol and a mixture containing 2-40% of glycol of aliphatic monohydric alcohol and glycol, and passing said mixture into a first separation stage; The above method, characterized in that it recirculates. 2. The separation of the mixture of glycol and aliphatic monohydric alcohol in the first stage is carried out with the production of an aliphatic monohydric alcohol and a mixture of glycol and aliphatic monohydric alcohol with a glycol content of 80-90%, Claim 1, wherein the separation of said mixture with a glycol content of 80-90% in the second stage is carried out with the formation of a mixture of aliphatic monohydric alcohol and glycol with a glycol content of 5-10%. the method of. 3. A process according to claim 1, wherein the second separation step is carried out upon heating the glycol to a temperature of up to 20° C. below its boiling point or the boiling point of the glycol.