JPS6364449B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyester with excellent transparency and color tone in a short time. Polyester, especially polyethylene terephthalate, is widely used as fibers, films, industrial materials, etc.Industrially, it is made into bis-(β -Hydroxyethyl) terephthalate (including its low polymers) is obtained and polycondensed in the presence of a catalyst at high temperature and under high vacuum to form a high polymer. It is well known that metal compounds such as zinc, calcium, antimony, cobalt, titanium, germanium, and tin are used as catalysts for direct esterification, transesterification, and polycondensation reactions during polyester production. On the other hand, when we examine catalysts that do not contain metals, we find hydrochloric acid and sulfuric acid, which are often used as catalysts for low-molecular esterification reactions, p-toluenesulfonic acid, known as direct esterification catalysts, and sulfonic camphor Brønsted acids such as No. 4640) certainly promote the esterification reaction, but their activity as polycondensation catalysts is low and have been considered unsuitable as catalysts for obtaining polyesters with a high degree of polymerization. However, the present inventors have discovered that certain sulfonic acid compounds have preferable polycondensation catalytic activity and provide polyesters with good color tone and transparency. That is, the present invention uses the following as a polycondensation catalyst when producing a polyester from terephthalic acid, a difunctional carboxylic acid containing terephthalic acid as a main component, or an ester-forming derivative thereof, and ethylene glycol or a glycol containing terephthalic acid as a main component. The gist of the present invention is a method for producing a polyester, which is characterized in that a sulfonic acid compound represented by the formula I or B or its intramolecular anhydride is used alone. ^{R 1} −SO ₃ X ○ ^{R 2} −( _{SO 3}
It may have a substituent selected from the group consisting of OH, NH ₂ , halogen, OSO ₃ H and morpholino group. ) _R ² : Alkylene group sexual derivative)
The technology of copolymerizing cationic dyes to produce easily dyeable polyesters with cationic dyes is well known. However, such metal salts of sulfonic acid have no polycondensation catalytic activity and do not fall within the category of sulfonic acid compounds as used in the present invention. Furthermore, a method is known in which a sulfonic acid compound called A-SO ₂ -OM (A: aliphatic group, M: hydrogen, alkali, or alkaline earth metal atom) is used together with a titanium compound as a polycondensation catalyst (Unexamined Japanese Patent Publication No. Showa 54-
No. 137094). However, the purpose of this technology is to obtain a homogeneous catalyst solution by using a sulfonic acid compound in combination, increase the softening point of the titanium-catalyzed polyester produced, improve thermal stability, and improve the yellow color. The purpose of this method is to improve the taste, and there is no description suggesting that the sulfonic acid compound promotes the polycondensation reaction, which is different from the method of the present invention in which a specific sulfonic acid compound is used as a polycondensation catalyst. Sulfonic acid compounds used in the present invention include methanesulfonic acid, ethanesulfonic acid,
Methionic acid, cyclopentanesulfonic acid, 1,1
-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,2-ethanedisulfonic anhydride, 1,
3-propanedisulfonic acid, sulfoacetic acid, β-sulfopropionic acid, isethionic acid, ethionic acid,
Ethionic anhydride, 3-oxy-1-propanesulfonic acid, propane sultone, butane sultone,
2-aminoethanesulfonic acid, 2-chloroethanesulfonic acid, chlorosulfonic acid, fluorosulfonic acid, trifluoromethanesulfonic acid, phenylmethanesulfonic acid, β-phenylethanesulfonic acid, α-phenylethanesulfonic acid, 2 -(N-
Examples include morpholino)ethanesulfonic acid, 3-(N-morpholino)propanesulfonic acid, ammonium chlorosulfonate, and triethylammonium ethanesulfonate. The amount of the sulfonic acid compound added varies depending on the type, but for sulfonic acid compounds having a halogen atom, it is 0.1 x 10 ^-4 mol to 10 x 10 ^-4 mol/mol of acid component, preferably 0.2 x 10 ^-4 mol. ~5×10 ^-4 mol/mol of acid component, 100 for other compounds
×10 ^-4 mole/acid component mole or less, preferably 50×
An appropriate addition amount may be selected within the range of 10 ^-4 mol/mol of acid component. If this sulfonic acid compound is added at the stage of transesterification or esterification reaction when a large amount of free ethylene glycol is present, many diethylene glycol units produced as a result of side reactions will be present in the resulting polyester, lowering the softening point. Therefore, if it is desired to obtain a polyester with a high softening point, a sulfonic acid compound may be added after the transesterification or esterification reaction. In addition, in order to obtain a polyester with a higher softening point, it is appropriate to employ the following method. A sulfonic acid compound is added to the esterification product with a relatively low esterification reaction rate of 88 to 94%, and polycondensation is carried out. A sulfonic acid compound is added to the transesterified or esterified product, which has a relatively high degree of polymerization and a concentration of glycolic OH groups of about 1.5 meq/g oligomer or less, and undergoes polycondensation. A sulfonic acid compound is added as an aqueous solution to the transesterified or esterified product to perform polycondensation. The method of the present invention uses not only polyethylene terephthalate but also isophthalic acid, p-
It can also be applied to the production of polyesters containing oxybenzoic acid, 5-sodium sulfoisophthalic acid, adipic acid, propylene glycol, trimellitic acid, pentaerythritol, 1,4-cyclohexanedimethanol, etc. as copolymerization components. Further, additives such as transesterification and esterification reaction catalysts, stabilizers such as phosphorus compounds, color improvers such as fluorescent agents, and pigments such as titanium dioxide may be present together. Next, the method of the present invention will be described with reference to Examples, but the present invention is not limited thereto. In the Examples, the intrinsic viscosity [η] of the polyester is a value measured at a temperature of 20° C. using an equiweight mixture of phenol and tetrachloroethane as a solvent. The amount of DEG was determined by quantifying ethylene glycol and diethylene glycol by gas chromatography after alkaline hydrolysis of polyester.
(denoted as DEG%). The color tone of the obtained polyester changes after molding into granules.
It was crystallized at 150°C±2°C for 1 hour and evaluated by determining L, a, and b values 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). As for the color tone of polyester, the larger the L value, the more the a value is 0.
The closer the b value is, and the smaller the b value is, unless it becomes extremely small, the better. Example 1 A slurry of terephthalic acid and ethylene glycol (ethylene glycol/terephthalic acid molar ratio 1.5) was continuously supplied to an esterification reactor in which bis(β-hydroxyethyl) terephthalate and its oligomers were present, and heated at 255°C. The esterification reaction was carried out under normal pressure for a residence time of 4.5 hours, and an esterification product with an esterification reaction rate of 93.5% was continuously obtained. To this esterification product, 40×10 ^-4 mol of ethanesulfonic acid was added per 1 mol of the acid component, and the pressure was gradually reduced in a glass polymerization tube to a final temperature of 0.1 mmHg.
Polycondensation was carried out at 285°C for 2 hours. The obtained polyester has [η] = 0.75, DEG%
= 3.1, L value = 84.5, a value = -1.8, b value = 2.3, and the product was almost colorless and had good transparency. Examples 2 to 22 and Reference Examples 1 to 6 Various sulfonic acid compounds were added to the esterified product obtained in Example 1 in varying amounts,
Table 1 shows the results of polymerization with different polymerization times. According to Table 1, if the amount of each sulfonic acid compound added is appropriate, a good polyester can be obtained, but if the amount added is too small, the polycondensation catalyst activity will be insufficient, and if it is too large, the color tone will deteriorate, and DEG %
It turns out that there are too many.

【table】

[Table] Example 23 1 mol of dimethyl terephthalate, 2 mol of ethylene glycol, and 1 x 10 ^-4 mol of zinc acetate were placed in a glass flask equipped with a fractionating tube and heated at 180°C under normal pressure.
The temperature was gradually increased from 230°C to 230°C, and the mixture was heated for 5 hours until the distillation of methanol was completed. This transesterified product was transferred to a glass polymerization tube, and 1×10 ^-4 mol of cobalt acetate (color improver) was added.
Trimethyl phosphate 3×10 ^-4 mol, 1,3-
After adding 20 × 10 ^-4 mol of propane disulfonic acid, the pressure was gradually reduced to a final value of 0.1 mmHg, and 275
Polycondensation was carried out at ℃ for 2 hours. The obtained polyester has [η] = 0.75, DEG%
= 3.0, L value = 80.2, a value = -0.6, b value = -1.1. Comparative Example 1 Example 23 was carried out under the same conditions as Example 23 except that 1,3-propanedisulfonic acid was not added. Polyester polymerization did not proceed, and [η] = 0.32, making it impossible to form chips. Example 24 A polyester was obtained in the same manner as in Example 23, except that 1,3-propanedisulfonic acid diammonium salt was used instead of 1,3-propanedisulfonic acid. The obtained polyester has [η] = 0.73, DEG%
= 2.6, L value = 79.5, a value = -0.5, b value = -0.2.

Claims (1)

[Scope of Claims] 1. As a polycondensation catalyst when producing polyester from terephthalic acid, a difunctional carboxylic acid containing terephthalic acid as the main component, or an ester-forming derivative thereof, and ethylene glycol or a glycol containing ethylene glycol as the main component. 1. A method for producing a polyester, characterized in that a sulfonic acid compound represented by the following formula (i) or (b) or its intramolecular anhydride is used alone. ^{R 1} −SO ₃ X ○ ^{R 2} −( _{SO 3}
It may have a substituent selected from the group consisting of OH, NH ₂ , halogen, OSO ₃ H and morpholino group. ) ^R2 : Alkylene group X: Hydrogen or _NY4 (Y is hydrogen and/or an alkyl group).