JPS6140246B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is intended for the production of polyester, and relates to a method of using ethylene glycol obtained by treating an ethylene glycol solution containing a phosphorus compound distilled in the polyester production process as part or all of the ethylene glycol charged by a specific method. To industrially produce polyesters, such as polyethylene terephthalate, bis-(β
-Hydroxyethyl) terephthalate or its lower polymers are usually polycondensed. Biaxially stretched films of such polyester, especially polyethylene terephthalate, have a high degree of crystallinity and a high softening point, and have excellent properties in terms of elongation, bending strength, chemical resistance, weather resistance, heat resistance, etc. It is widely used in industry. These polyester films are required to have surface properties suitable for each use, and surface properties are widely imparted by a so-called particle precipitation method. That is, a method in which a phosphorus compound is used together with a metal compound such as an alkali metal compound or an alkaline earth metal compound to precipitate these reaction products as fine particles during the polyester manufacturing process to impart desired characteristics, for example, JP-A-53 −
This method is described in Japanese Patent Application Laid-open No. 25694 and Japanese Patent Application Laid-Open No. 54-90294. Although this method is simple and can be easily adopted industrially, according to the knowledge of the present inventors, it has become clear that repeated polymerizations cause unexpected problems. That is, a part of the phosphorus compound added in the polyester manufacturing process is distilled out of the system together with ethylene glycol, and when this ethylene glycol is used, the phosphorus compound is added again to the polyester manufacturing process. If ethylene glycol containing phosphorus compounds as impurities is used as a feed ethylene glycol, the transesterification reaction will not proceed smoothly if the content is large, and even if the amount is relatively small, the transesterification reaction may occur. As a result, the particle size and amount of the precipitated particles change, making it impossible to obtain polyester with good reproducibility that gives the surface characteristics of depressions when formed into a film. The inventors of the present invention have conducted extensive studies in light of the above circumstances, and have determined that ethylene glycol, which contains a specific phosphorus compound that is easily distilled out from the polyester manufacturing process, is treated in a specific manner, thereby substantially affecting the precipitation of particles. If ethylene glycol whose phosphorus compound concentration has been reduced to the extent that it does not give any The present invention was completed based on the discovery that polyester can be produced economically. That is, when producing polyester, the present invention
Phosphorus compound expressed by the following formula distilled from the polyester manufacturing process

[Formula] (In the formula, R ¹ , R ² and R ³ each have 1 to 4 carbon atoms.
represents an alkyl group. ) is characterized by using ethylene glycol obtained by adding water in an amount equal to or more than the same volume as the ethylene glycol solution to an ethylene glycol solution containing one or more of the above, heating the mixture, and distilling off the phosphorus compound together with the water. It consists in a method for producing polyester. The present invention will be explained in more detail below. Various phosphorus compounds are added to the polyester manufacturing process depending on the purpose. Among these, phosphorus compounds with acidic hydroxyl groups, such as phosphoric acid, phosphorous acid, and acidic phosphate esters, are added to the reaction system. It reacts quickly with metal compounds present in the system, such as alkali metal compounds or alkaline earth metal compounds, and even if phosphorus compounds are present in excess, their vapor pressure is low and most of them are distilled out of the system. There is no. In the case of phosphorus compounds such as trialkyl phosphites such as trimethyl phosphite, triethyl phosphite and tributyl phosphite, the reaction rate with metal compounds and ethylene glycol is fast, and the amount distilled out of the reaction system is small. Even if a large amount of phosphorus is added and a portion of it is distilled out, it quickly reacts with ethylene glycol and turns into a phosphorus compound with a low vapor pressure, so it can be easily removed in the process of purifying the recovered ethylene glycol. Therefore, the effect of the present invention is exhibited in the polyester manufacturing process using trialkyl phosphates, especially phosphorus compounds represented by the following formula.

[Formula] (In the formula, R ¹ , R ² and R ³ each have 1 to 4 carbon atoms.
represents an alkyl group. ) For example, this is the case when one or more phosphorus compounds selected from the group consisting of trimethyl phosphate, triethyl phosphate, tributyl phosphate, dimethyl ethyl phosphate, diethyl methyl phosphate, etc. are added. That is, these phosphorus compounds are usually added after the end of the transesterification reaction or direct esterification reaction and before the beginning of the polycondensation reaction, but they have a relatively low boiling point,
For example, trimethyl phosphate and triethyl phosphate have temperatures of 192°C and 215°C, respectively, and their reaction rate with metal compounds and ethylene glycol is slow, so a considerable portion of trimethyl phosphate and triethyl phosphate leave the reaction system together with ethylene glycol until the end of the polycondensation reaction. I end up leaving. The concentration of phosphorus compounds in distilled ethylene glycol varies depending on the amount of phosphorus compounds added and reaction conditions, but it ranges from 20 to 20%.
Usually contains 5000ppm. Generally, ethylene glycol extracted and recovered from the polyester manufacturing process is sent to a distillation process to remove coexisting impurities such as small amounts of water, methanol, methyl cellosolve, and ethylene glycol monoacetate, but the vapor pressure of such phosphorus compounds Since many of these compounds are similar to those of ethylene glycol, it is impossible to reduce the concentration of phosphorus compounds by ordinary distillation operations. The present inventors conducted various studies on the removal of these phosphorus compounds, which are difficult to separate from ethylene glycol under normal conditions by distillation, and found that a large amount of phosphorus compounds were added to the ethylene glycol solution containing the phosphorus compounds. It has been found that if water is added and distillation is carried out, the phosphorus compound is distilled off along with the water, and the concentration of the phosphorus compound in ethylene glycol can be easily reduced. The amount of water used in the present invention is at least the same volume as the ethylene glycol solution containing the phosphorus compound,
Preferably 2 to 30 times the amount, more preferably 3 to 15 times the amount. If the volume is less than the same volume as the ethylene glycol solution, the amount of water is too small and the effects of the present invention are hardly exhibited. In addition, when distilling a mixed solution containing a phosphorus compound, ethylene glycol, and water, either a batch method or a continuous method may be adopted.
The distillation temperature at that time is around 100℃, for example 98~110℃
It is better to When such conditions are adopted, the trialkyl phosphate is distilled off together with the water, and the concentration of phosphorus compounds in the ethylene glycol of the bottoms is reduced to approximately 1/of the initial concentration.
It can be reduced by 2 to 1/10. Of course, water may be added to the ethylene glycol whose phosphorus compound concentration has been reduced and then distilled. In this case, the phosphorus compound concentration in the ethylene glycol of the bottoms can be more effectively reduced. Furthermore, during the distillation operation, an alkaline compound such as sodium hydroxide or potassium hydroxide may be present in the mixed solution. In this case, a portion of the trialkyl phosphate is decomposed during the distillation operation, so The object of the present invention can be effectively achieved. In this case, the amount of the alkali compound is preferably from equivalent to 100 times the amount of trialkyl phosphate, preferably from 3 to 30 times equivalent. In the present invention, it is possible to obtain a bottom liquor with a reduced concentration of phosphorus compounds, that is, an ethylene glycol solution, by such a method, and this may be used as it is as the charged ethylene glycol or a part thereof; If it contains an alkali metal salt or the like or diethylene glycol as an impurity, it is preferable to purify it by distillation under reduced pressure or normal pressure. By this method, the concentration of the phosphorus compound in the charged ethylene glycol can be reduced to a level that does not substantially affect the production of precipitated particles. Although this concentration depends on the conditions for obtaining the precipitated particles, it can be achieved, for example, by controlling the concentration of the phosphorus compound in the charged ethylene glycol to 30 ppm or less. In the present invention, charged ethylene glycol refers to all ethylene glycols used in the polyester manufacturing process, such as ethylene glycol used in transesterification or direct esterification, and ethylene glycol used for preparing catalysts and various auxiliaries. Of course, ethylene glycol obtained by the method of the present invention may be used in combination with unused high-purity ethylene glycol. The effects of the present invention are also exhibited when other phosphorus compounds such as phosphoric acid, phosphorous acid, and trialkyl phosphites are used together with the trialkyl phosphate. The present invention will be explained in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited to the following Examples. In the examples and comparative examples, "parts" indicate "parts by weight." The measurement method used is shown below. Coefficient of friction: Based on the method of ASTM D 1894-63, it has been improved so that it can be measured using a tape-shaped sample, and the measurement is performed at a temperature of 21±2℃ and a humidity of 65±5℃.
% atmosphere, the measurement conditions were a tensile speed of 40 mm/min, a chart speed of 120 mm/min, and the sample size was 15 mm in width and length.
A 150mm one was used. Number of surface protrusions: The number of surface protrusions of 0.05 μ or more per unit length (mm) on the surface of the biaxially stretched film was measured using a stylus-type surface roughness measuring machine manufactured by Taylor Bobson. Example 1 (A) 100 parts of dimethyl terephthalate, 68 parts of ethylene glycol, and 0.08 parts of calcium acetate monohydrate were placed in a reactor, heated to raise the temperature, and methanol was distilled off to perform a transesterification reaction, which was carried out for about 4 hours after the start of the reaction. It took a while to reach 225°C, and the transesterification reaction was substantially completed. Next, a solution prepared by dissolving 0.17 parts of triethyl phosphate and 0.04 parts of triethyl phosphite in 2 parts of ethylene glycol was added to the product after the transesterification reaction. Next, a solution of 0.04 part of antimony trioxide dissolved in 2 parts of ethylene glycol was added as a polymerization catalyst, and then polymerization was carried out in accordance with a conventional method. In other words, 100 minutes after adding antimony trioxide, the temperature in the system was increased to 285℃.
After the pressure reached 20 mmHg, the pressure was gradually reduced to 1 mmHg or less. After 4 hours, the pressure in the system was returned to normal and the polymer was discharged. Next, the obtained polymer was extruded into a sheet form from an extruder at 290°C, rapidly cooled to form an amorphous sheet, stretched at 95°C to 3.4 times in the longitudinal and transverse directions, and heat-treated at 230°C for 3 seconds. A film with a thickness of 25μ was obtained. The surface of the obtained film has favorable uniform fine irregularities, and the number of surface protrusions is 9/
It was warm in mm. The film has a friction coefficient of 0.9.
Both the feel and the appearance were excellent. (B) On the other hand, in order to recycle and reuse approximately 40 parts of ethylene glycol distilled during the production of polyester (A), that is, during transesterification and polycondensation, the concentration of phosphorus compounds in the ethylene glycol was determined by gas chromatography. However, 1600 ppm of triethyl phosphate was found, but no triethyl phosphite was detected. Next, 200 parts of water was added to this solution, and the temperature at the top of the column was set to 100-105°C, and simple distillation was carried out for about 1 hour. As a result, all of the distillate before distillation was It contains 61% of triethyl phosphate, and because some of it decomposes during distillation, the amount in the 40 parts of bottoms, which is mainly ethylene glycol, has decreased to only 15% of its pre-distillation content. Next, when 200 parts of water was added to the bottoms again and the same distillation operation was performed, the amount of phosphorus compounds contained in the second 40 parts of the bottoms was reduced to about 3% of the initial level. . Next, this bottoms was purified by distillation under reduced pressure of 15 mmHg to produce triethyl phosphate as the main fraction.
34 parts of recycled ethylene glycol containing 50 ppm was obtained. 34 parts of the regenerated ethylene glycol thus obtained and 38 parts of separately purified high-purity ethylene glycol containing no impurities such as phosphorus compounds were mixed, and this was used as the charged ethylene glycol for the second production of polyester. Note that this charged ethylene glycol was used not only for the transesterification reaction but also for the preparation of an ethylene glycol solution of a phosphorus compound and an antimony compound to be added after the transesterification reaction. In this case, no difference in transesterification reactivity was observed compared to when the high purity ethylene glycol was used as the total amount of ethylene glycol charged. Next, produce polyester in the same manner as in (A),
A polyester film was obtained using the polyester in the same manner as in (A). The surface condition of the polyester film is the same as (A), the number of surface protrusions is 9.5/mm, and the coefficient of friction is
0.9, and no difference was observed between them and the film (A). Comparative Example 1 Approximately 40 parts of ethylene glycol containing 1,600 ppm of triethyl phosphate distilled during polyester production in (B) of Example 1 was added to 15 parts of ethylene glycol without adding water.
Distillation was carried out under reduced pressure of mmHg to obtain 34 parts of regenerated ethylene glycol as the main fraction. This recycled ethylene glycol contained 1550 ppm of triethyl phosphate. Next, 34 parts of this recycled ethylene glycol and 38 parts of high-purity ethylene glycol were mixed, and this was used as the charged ethylene glycol to produce polyester in the same manner as in Example 1 (B). However, in this case, the transesterification reaction did not proceed smoothly and polyester could not be obtained, so 5 parts of the recycled ethylene glycol and 67 parts of high-purity ethylene glycol were mixed again and this was used as the charged ethylene glycol Example 1 Polyester and film were produced in the same manner as in (B). In this case, although the proportion of regenerated ethylene glycol in the charged ethylene glycol was small, the transesterification reaction rate was rather slow and it took about four and a half hours to complete the reaction. Although many uniform and fine irregularities were observed on the surface of the obtained film, the average size was smaller than that of the film (A) of Example 1, and the number of surface protrusions was 3. It was hot in pieces/mm. Further, the coefficient of friction of the film was 1.3, and the slipperiness was extremely poor.

Claims (1)

[Claims] 1. When producing polyester, a phosphorus compound represented by the following formula distilled from the polyester production process [Formula] (wherein R ¹ , R ² and R ³ each have 1 to 4 carbon atoms)
represents an alkyl group. ) is characterized by using ethylene glycol obtained by adding water of the same volume or more as the ethylene glycol solution to an ethylene glycol solution containing one or more of the following, heating the mixture, and distilling off the phosphorus compound along with the water. Method of manufacturing polyester. 2. In the method described in claim 1,
A method characterized in that the amount of water is 2 to 30 times the amount of the ethylene glycol solution. 3. The method according to claim 1 or 2, characterized in that an alkali compound is added to the distilled ethylene glycol solution together with water. 4. The method according to claim 3, wherein the amount of the alkali compound is equivalent to to 100 times the amount of the phosphorus compound contained in the distilled ethylene glycol solution.