JPS6254130B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a high melting point polyester which has excellent transparency and has a small amount of diethylene glycol component in the polymer. Polyester, especially polyethylene terephthalate, is widely used as fibers, films, industrial materials, etc.Industrially, it is produced by directly esterifying or transesterifying terephthalic acid or dimethyl terephthalate and ethylene glycol. It is produced by a method in which ethyl 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. Metal compounds such as antimony, titanium, germanium, tin, and zinc are well known as polycondensation catalysts. Among these compounds, antimony compounds have a disadvantage in that the resulting polymer has poor transparency and a dark, dull yellowish-greenish color tone, while titanium, tin, and zinc compounds have a disadvantage in that the polymer has a marked yellowish tinge. Although germanium compounds give polymers with relatively good color, they have problems in that they are expensive and tend to distill out of the reaction system during polymerization, making it difficult to control the polymerization. In addition, a common problem when using metal compounds as catalysts is that the metal compounds precipitate as insoluble substances during the polyester production reaction, adhere to the inner walls of reaction vessels and piping, peel off, and get mixed into the polymer. The quality may be lowered by doing so. Since such a phenomenon does not occur with catalysts that do not contain metals, polymers produced using such catalysts are suitable for molding products such as transparent films and bottles, where contamination by foreign matter can be a fatal defect. It is particularly preferred as a raw material for products. Of course, there are also great advantages when adding pigments such as titanium oxide or when using it for textiles. It is well known that Lewis acids such as metal compounds are used as catalysts for direct esterification, transesterification, and polycondensation reactions during polyester production. On the other hand, Brönsted compounds such as p-toluenesulfonic acid and sulfonic camphor (Japanese Patent Publication No. 4640/1989), which are known as direct esterification catalysts for glycol and hydrochloric acid, sulfuric acid or terephthalic acid, which are often used as catalysts for esterification reactions of low molecules, Although acids do promote esterification reactions, their activity in polycondensation reactions is low, making them unsuitable as catalysts for obtaining polymers with a high degree of polymerization. However, according to studies conducted by the present inventors, it has been found that aromatic sulfonic acid compounds having no other substituents or having a specific nuclear substituent have significant polycondensation activity. However, such aromatic sulfonic acid compounds have the drawback that the amount of diethylene glycol component in the produced polymer is large compared to other known metal compound catalysts, and the softening point of the polymer is lowered. As a result of further investigation, it was discovered that when an ammonium salt of a specific aromatic sulfonic acid was used as a catalyst, the amount of diethylene glycol component in the polymer was significantly reduced. That is, the present invention provides a method for producing 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, using the following formula as a catalyst. A method for producing a polyester, characterized in that the following ammonium sulfonate salt is added in an amount such that the ammonium sulfonate base is 1 x 10 ^-4 to 10 x 10 ^-4 equivalent mole per 1 mole of the acid component constituting the polyester. be. Formula (X) _-o Ar-( _SO3NR4 )m m: 1-3, n: 0-3 Ar: aromatic group, X: ^OR1 , ^COOR2 , halogen R: hydrogen, alkyl _group , aryl group However, R ¹ and R ² are hydrogen or lower alkyl groups. n=0 indicates that there is no nuclear substituent other than the ammonium sulfonate base. When n≧2, X may be the same or different. In this method, if the amount of the ammonium sulfonate compound added is less than 1×10 ^-4 equivalent mole/mole of the acid component, the polymerization activity will be insufficient and it will be difficult to obtain a polymer with a high degree of polymerization. If the amount exceeds ×10 ^-4 equivalent mole/mole of acid component, the yellow coloration of the polymer becomes significant, which is not preferable. In addition, technology for producing easily dyeable polyester with cationic dyes by copolymerizing an alkali or alkaline earth metal salt of aromatic sulfonic acid having an ester-forming group (for example, 5-sodium sulfoisophthalic acid or its ester-forming derivative) is well known. However, such metal salts of sulfonic acids do not have any polycondensation activity, and in order to develop sufficient dyeing properties, they must be added in an amount of about 5 x 10 ^-3 mol or more per mol of acid component constituting the polymer. Because of the necessity, this method is completely different from the method of the present invention. Examples of the sulfonic acid ammonium salts used in the present invention include the following sulfonic acid ammonium salts, mono-, di-, tri- or tetraalkylammonium salts, aniline salts and other arylamine salts. Sulfonic acids: benzene sulfonic acid, m- or p-benzenedisulfonic acid, 1,3,5-benzenetrisulfonic acid, o-, m- or p-sulfobenzoic acid, anisole-o-sulfonic acid, 1,5
- naphthalenedisulfonic acid, o-, m- or p
-chlorobenzenesulfonic acid, o-, m- or p-bromobenzenesulfonic acid, o-, m- or p-fluorobenzenesulfonic acid, 4-chloro-3-methylbenzenesulfonic acid, chlorobenzene-1,4-disulfonic acid , 1-chloronaphthalene-4-sulfonic acid, 2-chloro-4-sulfobenzoic acid, 4-chloro-2-sulfobenzoic acid, 4-
Chloro-3-sulfobenzoic acid, 5-sulfosalicylic acid, etc. The method of the present invention uses not only polyethylene terephthalate but also isophthalic acid, p-
Oxybenzoic acid, 5-sodium sulfoisophthalic acid, adipic acid, propylene glycol, 1,
It can also be applied to the production of polyesters containing 4-cyclohexanedimethanol, trimellitic acid, pentaerythritol, etc. as copolymer components. Further, additives such as a catalyst for monomer synthesis, a stabilizer such as a phosphorus compound, a color improver such as a fluorescent agent, and a pigment such as titanium dioxide may coexist. 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 polymer is a value measured at a temperature of 20° C. using a mixture of equal weights of phenol and tetrachloroethane as a solvent. The diethylene glycol component content in the polymer is determined by quantifying ethylene glycol and diethylene glycol by gas chromatography after alkaline hydrolysis of the polymer, and is expressed as mol% of diethylene glycol (denoted as DEG%) based on the total glycol. The color tone of the obtained polymer changes at 150℃ after molding into granules.
Crystallize at ±2°C for 1 hour and use a colorimeter to measure L,
Evaluation was made by determining a and b values. 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 the polymer, the larger the L value, the more a
The closer the value is to 0, 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 and the esterification reaction was carried out at 250°C and under normal pressure for a residence time of 5 hours, resulting in a reaction rate of 93%.
of esterified products were obtained continuously. To this esterification product, 4×10 ^-4 mol of ammonium p-sulfobenzoate was added per 1 mol of the acid component, and the final product was reduced under reduced pressure in a glass polymerization tube.
Polycondensation was carried out at 0.1 mmHg and 285°C for 2 hours. The obtained polymer has [η] = 0.70, DEG% =
2.6, L value = 84.1, a value = -1.6, b value = 2.0, and the product had good transparency. Reference Example 1 Example 1 was carried out under the same conditions as in Example 1 except that p-sulfobenzoic acid was used instead of ammonium p-sulfobenzoate. The obtained polymer had [η] = 0.71, DEG% =
5.3, L value = 83.9, a value = -1.5, b value = 1.8, and the DEG% was higher than that of the polymer obtained in Example 1. Examples 2 to 10 and Comparative Examples 1 to 2 Various ammonium sulfonate salts were added to the esterified product obtained in Example 1 in different amounts, and the polymerization time was changed to perform polymerization. The results are shown in the table. . According to this, if the amount of ammonium sulfonate salt added is too small, the polymerization activity will be insufficient.
If the amount is too high, the polymer will be colored yellow, which is undesirable.

【table】

[Table] Example 11 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. The transesterified product was transferred to a glass polymerization tube, 1 x 10 ^-4 mol of ammonium 1,3,5-benzenetrisulfonate and 4 x 10 ^-4 mol of trimethyl phosphate were added, and the pressure was gradually reduced. The final pressure was set to 0.1 mmHg, and the polycondensation reaction was carried out at 285°C for 2 hours. The obtained polymer has [η] = 0.70, DEG% =
2.7, L value = 83.8, a value = -1.6, and b value = 2.1.

Claims (1)

[Scope of Claims] 1. 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 terephthalic acid as the main component, the following catalyst may be used as a catalyst: The ammonium sulfonate salt represented by the formula is 1x
A method for producing polyester, which comprises adding the polyester in an amount of 10 ^-4 to 10×10 ^-4 equivalent moles. Formula (X) _-o Ar-( _SO3NR4 )m m: 1-3, n: 0-3 Ar: aromatic group, X: ^OR1 , ^COOR2 , halogen R: hydrogen, alkyl _group , aryl group However, R ¹ and R ² are hydrogen or lower alkyl groups. n=0 indicates that there is no nuclear substituent other than the ammonium sulfonate base. When n≧2, X may be the same or different.