JPS6136529B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing polyester that has excellent transparency and color tone 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 made into bis(β- It is produced by a method in which 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. 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 significant yellowish tinge to the polymer. Although germanium compounds give polymers with relatively good color, 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 the reaction vessel and piping, and peel off, causing the metal compounds to dissolve into the polymer. This can lead to a decrease in quality due to contamination. 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. 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, aromatic sulfonic acid compounds having no other substituents or having a specific substituent have remarkable polycondensation activity and are capable of producing polymers with good color tone. I understood. However, such aromatic sulfonic acid compounds have the drawback that the amount of diethylene glycol component in the produced polymer is larger than that of other known metal compound catalysts, resulting in a lower softening point of the polymer. As a result of further investigation, we found that when a polycondensation reaction is carried out using an aromatic sulfonic acid compound as a catalyst, the amount of diethylene glycol in the polymer decreases significantly when a specific amount of an amine compound is present. It has been found that polymers with similar amounts of diethylene glycol components can be obtained. That is, the present invention uses a sulfonic acid compound represented by the following formula as a catalyst when producing polyester from a difunctional carboxylic acid containing terephthalic acid as a main component or an ester-forming derivative thereof and a glycol containing ethylene glycol as a main component. The amount of the sulfonic acid group is 1 x 10 ^-4 to 10 x 10 ^-4 equivalent mole per mol of the acid component constituting the polyester, and the amount of the amine is 0.2 to 4 times the basic nitrogen atom of the sulfonic acid group. This is a method for producing polyester, characterized in that it is added in an amount of 0.4 to 2 moles, preferably 0.4 to 2 times the mole. Formula (X) _-o Ar( _-SO3H )m m: 1-3, n: 0-3 Ar: aromatic group X: _OR1 , _COOR2 , halogen However, _R1 and _R2 are hydrogen or lower It is an alkyl group. n=0 indicates that there is no substituent other than the sulfonic acid group. When n≧2, X may be the same or different. If the amount of basic nitrogen atoms in the amine compound is less than 0.2 times the mole of the sulfonic acid group, it is difficult to see the effect of suppressing the amount of diethylene glycol component, and if the amount exceeds 4 times the amount of the sulfonic acid group, the polymerization of the sulfonic acid compound will decrease. This is not preferred because it inhibits the condensation activity and gives the product a yellowish tinge. If the amount of aromatic sulfonic acid compound added is less than 1 x 10 ^-4 mol/mol of acid component, the polymerization activity will be insufficient, it will be difficult to obtain a polymer with a high degree of polymerization, and the reaction will take a long time. Has a yellowish tinge. If the amount of the aromatic sulfonic acid compound added exceeds 10 x 10 ^-4 mol/mol of acid component, the polymer will be colored yellow and the amount of diethylene glycol component will increase, which is not preferred. In addition, a metal salt of an aromatic sulfonic acid having an ester-forming group (for example, 5-sodium sulfoisophthalic acid or its ester-forming derivative)
The technology of copolymerizing cationic dyes to produce easily dyeable polyesters with cationic dyes is well known. However, such metal salts of sulfonic acids do not have any polycondensation activity, and in order to develop sufficient dyeing properties, 5×
Since it is necessary to add about 10 ^-3 mol or more,
This method is completely different from the method of the present invention. The amines used in the present invention include methylamine, ethylamine, n-propylamine, and n-propylamine, which are primary amines among aliphatic monoamines.
-butylamine, 2-hexylamine, nonylamine, allylamine, secondary amines dimethylamine, diethylamine, di-isopropylamine, tertiary amine trimethylamine,
N/N-dimethylpropylamine, quaternary ammonium compounds such as tetramethylammonium hydroxide and tetraethylammonium hydroxide, aliphatic polyamines such as ethylenediamine and hexamethylenediamine, amino alcohols such as 2-aminoethanol, and alicyclic amines. cyclohexylamine, dicyclohexylamine, N.N-dimethylcyclohexylamine, aromatic amine aniline, p-toluidine, N
Examples include compounds such as -methylaniline, diphenylamine, p-phenylenediamine and p-aminobenzoic acid. Aromatic sulfonic acid compounds include benzenesulfonic 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, chlorobenzenesulfonic acid 1,4-disulfonic acid,
Examples include 1-chloronaphthalene-4-sulfonic acid, 2-chloro-4-sulfobenzoic acid, 4-chloro-2-sulfobenzoic acid, 4-chloro-3-sulfobenzoic acid, and 5-sulfosalicylic acid. The presence of free ethylene glycol at the beginning of the polycondensation reaction increases the amount of diethylene glycol produced, so it is preferable to add the aromatic sulfonic acid compound as a solid or as an aqueous solution. 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 during monomer synthesis, a stabilizer such as a phosphorus compound, a color improver such as a cobalt compound or a fluorescent agent, and a pigment 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 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 diethylene glycol is expressed as mole% (denoted as DEG%) based on the total glycol.
This is what is shown. 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 determine
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). The color tone of the polymer is better as the L value is larger, the a value is closer to 0, and the b value is smaller unless it becomes extremely small. 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℃ and under normal pressure for a residence time of 6 hours, resulting in a reaction rate of 96%.
of esterified products were obtained continuously. 3 x 10 ^-4 mol of p-sulfobenzoic acid and 4 x 10 ^-4 mol of diethylamine were added to this esterified product per 1 mol of the acid component, and the pressure was reduced to 0.1 mmHg in a glass polymerization tube. Polycondensation was carried out at 285°C for 2 hours. The obtained polymer had [η] = 0.68, DEG% =
2.5, L value = 83.6, a value = 1.5, b value = 1.3,
The product was almost colorless and had good transparency. Examples 2 to 11 and Comparative Examples 1 to 4 Table 1 shows the results of polymerization by changing the amounts of various aromatic sulfonic acid compounds and amines added to the esterified product obtained in Example 1 and changing the polymerization time. Shown below.

[Table] As is clear from Table 1, if the amount of the sulfonic acid compound added is too small, the polymerization activity will be insufficient.
If it is too large, the color tone of the polymer will be poor and the DEG% will increase. Furthermore, if the amount of amine added to the sulfonic acid compound is too small, DEG% will increase, and if it is too large, polymerization activity will be inhibited and the color tone of the polymer will deteriorate. Example 12 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 to 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 x 10 ^-4 mol of cobalt acetate and 2-chloro-4
- 3 x 10 ^-4 mol of sulfobenzoic acid, 4 x 10 ^-4 mol of trimethyl phosphate and 3 mol of diphenylamine
After adding x10 ^-4 mol, the pressure was gradually reduced to 0.1 mmHg and a polycondensation reaction was carried out at 275°C for 2 hours. The obtained polyester has [η] = 0.69, DEG%
= 2.8, L value = 78.5, a value = -0.7, b value = -1.2. Comparative Example 5 This was carried out under the same conditions as in Example 12 except that diphenylamine was not added. The obtained polyester has [η] = 0.69, DEG%
= 5.2, L value = 78.7, a value = -0.6, b value = -1.2, DEG% lower than the polymer obtained in Example 12.
has become more common.

Claims (1)

[Scope of Claims] 1. A sulfone represented by the following formula as a catalyst when producing polyester from a difunctional carboxylic acid containing terephthalic acid as a main component or its ester-forming derivative and a glycol containing ethylene glycol as a main component. The acid compound has a sulfonic acid group of 1 x 10 ^-4 to 1 mole of the acid component constituting the polyester.
1. A method for producing a polyester, which comprises adding an amine in an amount of 10×10 ⁻⁴ equivalent mole and an amount of amine whose basic nitrogen atom is 0.2 to 4 times the mole of sulfonic acid group. Formula (X) _-o Ar( _-SO3H )m m: 1-3, n: 0-3 Ar: aromatic group X: _OR1 , _COOR2 , halogen However, _R1 , _R2 are hydrogen or lower It is an alkyl group. n=0 indicates that there is no substituent other than the sulfonic acid group. When n≧2, X may be the same or different.