JPH0318651B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for storing a catalyst solution containing an antimony compound and a phosphorus compound, which makes it possible to produce a polyester with excellent color tone, transparency, and thermal stability. Polyesters, especially polyethylene terephthalate, are very useful polymers as fibers or films, and many methods are already known for their production. In the production of polyester,
It is necessary to use a polycondensation catalyst, but antimony compounds, especially antimony trioxide, are the most widely used because they have excellent catalytic activity and are inexpensive. At the same time, phosphorus is used as a thermal stabilizer during polycondensation. Methods using combinations of compounds are widely used. However, when an antimony compound is used as a polycondensation catalyst and a phosphorus compound is used as a thermal stabilizer, the phosphorus compound and antimony compound react in a complicated manner to form insoluble fine particles, and as a result, the resulting polyester is known to impair transparency. In addition, phosphorus compounds such as alkyl esters of phosphoric acid, which are commonly used as thermal stabilizers, tend to scatter out of the system during the polycondensation reaction, resulting in the problem that they must be added in large amounts. Regarding this point, as a result of various studies, the present inventors found that if phosphoric acid is used as the phosphorus compound, there is almost no scattering during the polycondensation reaction, but if phosphoric acid is simply used in combination with an antimony compound, The disadvantage was that the transparency was even worse than when alkyl esters were used. The present inventors conducted various studies in order to eliminate the above-mentioned drawbacks when producing polyester using a combination of phosphoric acid and an antimony compound. As a result, the inventors of the present invention treated phosphoric acid in advance under refluxing glycol, and added antimony to the treatment solution. We found that this problem could be solved all at once by adding a catalyst solution obtained by adding the compound to the reaction system and polycondensing it, and proposed it earlier. However, although the catalyst solution prepared in this way shows good results when used within a short period of time after preparation, if it is stored at room temperature for a long period of time, it becomes It has been found that some kind of reaction occurs between the antimony compounds, causing problems such as the formation of insoluble fine particles in the system and loss of catalytic activity. In view of the above circumstances, the present invention has been made through further extensive research, and the present invention has been completed by discovering the fact that by thermally storing the catalyst solution, no insoluble particles are generated and the catalyst is not deactivated. It came to this. That is, the present invention heat-treats a glycol solution of phosphoric acid while refluxing the glycol, and stores a catalyst solution for polyester production prepared by adding an antimony compound to the treated solution at a temperature of 50 to 200°C. It is characterized by being maintained at a certain temperature. Examples of the antimony compound used in the present invention include conventionally known antimony compounds such as antimony trioxide, antimony chloride, and antimony acetate, but as mentioned above, antimony trioxide is preferred. In the present invention, phosphoric acid is used as a thermal stabilizer, but as mentioned above, it does not scatter out of the reaction system during polycondensation, so it has the advantage of requiring less addition than conventional phosphorus compounds. . In the present invention, the glycol used for preparing the catalyst solution is preferably the same as the glycol component constituting the polyester to be produced,
Ethylene glycol is particularly desirable. In addition, the reflux treatment with glycol should be carried out for at least 10 minutes, preferably
It is preferable to do this for 30 minutes or more. If the reflux time is less than 10 minutes, the treatment liquid itself becomes cloudy upon addition of the antimony compound to the treatment liquid, which is not preferable. In the present invention, there is no particular restriction on the concentration of phosphoric acid when refluxing the phosphoric acid as a glycol solution, but a range of 0.1 to 10 mol% is usually suitable. If the phosphoric acid concentration is less than 0.1 mol%, the amount of glycol will inevitably increase in order to obtain a sufficient color tone improvement effect, which will cause problems when adding it to the reaction system. On the other hand, if the phosphoric acid concentration is higher than 10 mol %, the reflux time needs to be longer than necessary, which has the drawback of increasing the cost of preparing the catalyst solution. In the present invention, the antimony compound can be added to the treatment solution of the phosphoric acid glycol solution by directly adding the antimony compound alone, but preferably by adding the antimony compound dispersed or dissolved in the glycol. The present invention utilizes the catalyst solution prepared in this manner.
It is characterized by being stored at a temperature of 50 to 200°C, with a particularly preferred storage temperature being 120 to 180°C.
It is. If this temperature is lower than 50°C, sufficient effects will not be exhibited, and if this temperature is higher than 200°C, undesirable reactions will occur. In addition, a glycol solution containing an antimony compound, a cobalt compound, and a phosphorus compound was heated at 70 to 120°C.
A method of insulating and storing the antimony compound at a temperature of This tendency was strong. However, as in the present invention, the above-mentioned problems can be solved by treating phosphoric acid with glycol under specific conditions in advance and then maintaining the catalyst solution to which an antimony compound has been added at a high temperature. The catalyst solution is added to the reaction system when the transesterification reaction or esterification reaction is almost completed;
In other words, this is the point when the reaction rate reaches 90% or more. In addition, the amount of antimony compound added to the reaction system is determined based on the total acid components that make up the polyester.
0.001 to 0.1 mol%, and phosphoric acid is 0.005 to 0.1
The amount is preferably mol %. If the amount of antimony compound added is less than 0.001 mol%, polycondensation will not proceed smoothly, and if the amount of phosphoric acid added is less than 0.001 mol%,
If it is less than 0.005 mol%, a satisfactory color tone improvement effect cannot be obtained. In addition to polyethylene terephthalate homopolyester, the polyester produced using such a catalyst solution includes isophthalic acid, 5-sodium sulfoisophthalic acid, naphthalene-2,6-dicarboxylic acid, adipic acid, and sebacine as a third component. dibasic acids such as acids, oxyacids such as p-oxybenzoic acid, p-oxyethoxybenzoic acid,
Polymethylene glycols such as trimethylene glycol and 1,4-butanediol, polyethylene glycols such as diethylene glycol and triethylene glycol, polyols such as propylene glycol, cyclohexane-1,4-dimethanol, and pentaerythritol, and ester-forming derivatives thereof are copolymerized. Examples include polyester. Furthermore, when producing polyester, various additives such as titanium dioxide as a dissipating agent, silicon dioxide as a lubricant, and various coloring pigments for the purpose of coloring can be added. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. In addition, the intrinsic viscosity [η] of the polyester in the example is
It was determined from the solution viscosity measured at 20°C using a mixed solvent of equal weights of phenol and tetrachloroethane. The color tone of the polyester was determined by visually observing its transparency in a molten state, and after crystallizing the chip at 150° C. for 1 hour, the L, a, and b values were determined using a color difference meter. The L value is the lightness (the larger the value, the brighter), the a value is the red-green hue (+ is reddish, - is greenish), and the b value is the yellow-blue hue (+ is yellowish, - is bluish). Regarding the color tone of the polymer, it is preferable that the L value is large, the a value is close to 0, and the b value is small as long as it does not become extremely large on the negative side. Example (a) Preparation of catalyst solution A 1 mol% ethylene glycol solution of phosphoric acid
A separately prepared 1 mol % ethylene glycol solution of antimony trioxide was added to and mixed with a treatment solution that had been refluxed at a temperature of 200° C. for 1 hour. (b) Storage of catalyst solution The catalyst solutions prepared in (a) above were thermally stored at room temperature at the temperatures shown in Table 1 for 3 days and 7 days, respectively. (c) Production of polyester A slurry of terephthalic acid and ethylene glycol in a molar ratio of 1:1.6 was continuously supplied to an esterification reactor containing bis(β-hydroxyethyl) terephthalate and its oligomer, and 260
The esterification reaction was carried out at ℃ and normal pressure for a residence time of 6 hours to continuously obtain an esterified product with a reaction rate of 95%. This esterification product is transferred to a glass polymerization reactor and stored in the above (b) so that antimony trioxide is 2 x 10 ^-4 mol and phosphoric acid is 5 x 10 ^-4 mol per 1 mol of acid component. Add the catalyst solution
Start depressurizing at 285°C, and reduce the pressure to 2 with a final decompression degree of 1 Torr.
Time polycondensation was carried out. Table 1 shows the obtained polyester characteristic values. All of the molten polyesters during polycondensation were transparent and showed no dullness at all.

[Table] Comparative Example 1 A catalyst solution was prepared from phosphoric acid and an antimony compound in the same manner as in Example (a), stored at room temperature and normal pressure for 3 days, and used to prepare the catalyst solution in Example (H). Polyester was produced in the same manner as in ). [η] of the obtained polyester was 0.68. In addition, insoluble fine particles have already precipitated in the catalyst solution on the first day of storage after preparation, and the molten polyester during polycondensation has a dull color tone, and the color tone of the chips has an L value of 63.7 and an a value of 1.3. , the b value was 2.4. Comparative Example 2 A catalyst solution was obtained by mixing a separately prepared 1 mol% ethylene glycol solution of phosphoric acid and a 1 mol% ethylene glycol solution of antimony trioxide at room temperature, then heating and keeping the mixture at 150°C and storing it for 3 days. no(ha)
Polyester was produced by adding it to the reaction system in the same manner as above. The color tone of the molten polyester during polycondensation is dull, and the color tone of the chips has an L value of 54.3 and an a value.
1.3, and the b value was 2.9, which was not good.

Claims (1)

[Claims] 1. When storing a catalyst solution for polyester production prepared by heat-treating a glycol solution of phosphoric acid while refluxing the glycol and adding an antimony compound to the treated solution, a temperature of 50 to 200°C is required. A method for storing a catalyst solution for polyester production, characterized by maintaining the catalyst solution at a temperature of . 2. The method according to claim 1, wherein the glycol is ethylene glycol.