JPS6136777B2 - - 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. Polyesters, especially polyethylene terephthalate, are widely used as fibers, industrial materials, etc., and industrially, bis(β-hydroxyethyl) is produced by direct esterification or transesterification from terephthalic acid or dimethyl terephthalate and ethylene glycol. It is produced by a method in which terephthalate (including its low polymers) is obtained and polycondensed in the presence of a catalyst at high temperature and 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 the disadvantage that the resulting polyester has poor transparency and a dark, dull, yellowish-greenish color tone, while titanium, tin, and zinc compounds have the disadvantage that the polyester has a marked yellowish tinge. If a germanium compound is used, a polyester with a relatively good color tone can be obtained, but there are problems in that it is expensive, and it is difficult to control the polymerization because it tends to distill out of the reaction system during polymerization and the catalyst concentration changes. In addition, a common problem when using metal compounds as catalysts is that the metal compounds are precipitated as insoluble substances during the polyester production reaction, adhere to the inner walls of the reaction vessel and piping, peel off, and get mixed into the polyester. There are times when the quality is lowered. Such a phenomenon is unlikely to occur with catalysts that do not contain metals, so polyether produced using such catalysts is suitable for use in transparent films and bottles, for example, where contamination by foreign matter can be a fatal defect. It is particularly preferred as a raw material for molded 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 ions are used as catalysts for direct esterification, transesterification, and polycondensation reactions during polyester production. On the other hand, P-toluenesulfonic acid and sulfonic acid camphor (Japanese Patent Publication No. 1983-1999) are known as catalysts for the direct esterification of glycol with hydrochloric acid, sulfuric acid, or terephthalic acid, which are often used as catalysts for the esterification reaction of low-molecular-weight carboxylic acids with alcohols. No. 4640)
Although Bronsted acids such as Brønsted acids do promote the esterification reaction, their activity in the polycondensation reaction is low, making them unsuitable as catalysts for obtaining polyesters 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 nuclear substituent not only have remarkable polycondensation activity but also produce 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. Therefore, as a result of further investigation, we used direct esterification or transesterification products (hereinafter referred to as oligomers) with a high reaction rate and few glycol end groups, in other words, a relatively high average degree of polymerization, to achieve the aromatic We have found that when a polycondensation reaction is carried out using a sulfonic acid compound as a catalyst, the amount of diethylene glycol in the polymer is significantly reduced, and a polymer with the same amount of diethylene glycol as in the case of using a known metal compound can be obtained. That is, the present invention is an oligomer obtained by reacting a difunctional carboxylic acid containing terephthalic acid as a main component or an ester-forming derivative thereof with a glycol containing ethylene glycol as a main component, the reaction rate of which is 96% or more, And to a product in which the amount of glycol end groups is 1.5 milliequivalent or less per gram of oligomer, a sulfonic acid compound represented by the following formula is added at 1×10 ^- The gist of this invention is a method for producing polyester, which is characterized in that the polyester is added in an amount of ⁴ to 10 x 10 ^-4 equivalent moles and a polycondensation reaction is carried out. Formula (X)- _o A _r (-SO ₃ H) _n m: 1 to 3, n: 0 to 3 A _r : Aromatic group X: OR ₁ , COOR ₂ , halogen However, R ₁ and R ₂ are hydrogen or It is a lower alkyl group. n=0 indicates that there is no nuclear substituent other than the sulfonic acid group. When n≧2, X may be the same or different. It is expected that if an oligomer with a high reaction rate and a small amount of glycol end groups is used, a polymer with a small amount of diethylene glycol component can be obtained. However, when the sulfonic acid compound of the present invention is used as a catalyst than when a known metal compound is used as a catalyst, the amount of glycol end groups in the oligomer has a greater effect on the amount of diethylene glycol component in the polymer. By using a small amount of oligomer, it is possible to obtain a polymer containing a diethylene glycol component that is so low as to be unimaginable from the behavior when known metal compounds are used. For example, oligomers with a low degree of polymerization are prepolycondensed without a catalyst to prepare various oligomers with different amounts of glycol end groups, and antimony trioxide (2×
10 ^-4 mol/mol of acid component), cobalt acetate (4×
The glycol terminal of the oligomer when polycondensed at 275°C for 2 hours using a sulfonic acid compound (4 x ^{10 -4} mol/mol of acid component) described in the Examples described later as a catalyst. The relationship between the amount of groups [OH] and the component amount DEG% of diethylene glycol in the produced polymer is shown in FIG. When polycondensation is carried out using a sulfonic acid compound as a catalyst, the amount of glycol end groups per gram of oligomer is 1.5.
Use of oligomers exceeding milliequivalents is not preferred because the amount of diethylene glycol component in the polymer increases. Furthermore, if the reaction rate is less than 96%, a polymer with a high degree of polymerization may not be obtained. If the amount of sulfonic acid groups in the aromatic sulfonic acid compound to be added is less than 1×10 ^-4 equivalent mole/mole of acid component, the polycondensation activity will be insufficient and it will be difficult to obtain a polymer with a high degree of polymerization. The reaction takes a long time, resulting in a yellowish tinge. The amount of sulfonic acid groups in the aromatic sulfonic acid compound to be added is 10 × 10 ^-4 equivalent mole/
If the amount exceeds the molar amount of the acid component, the polymer will be colored yellow and the amount of diethylene glycol component will increase, which is not preferable. It should be noted that the technique of producing a polyester easily dyeable with cationic dyes by copolymerizing a metal salt of an aromatic sulfonic acid compound having an ester-forming group (for example, 5-sodium sulfoisophthalic acid or its ester-forming derivative) is well known. It is being However, such metal salts of sulfonic acids have no polycondensation activity at all, and in order to develop sufficient dyeing properties, sulfonic acid metal salts must be
This method is completely different from the method of the present invention because it requires addition of approximately ×10 ^-3 mol or more. Aromatic sulfonic acid compounds used in the present invention 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-
Examples include 3-methylbenzenesulfonic acid, chlorobenzene-1,4-disulfonic acid, 1-chloronaphthalene-4-sulfonic acid, 2-chloro-4-sulfobenzoic acid, and 5-sulfosalicylic acid. 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 reaction rate was calculated based on the following formula. Reaction rate = [COO] - [A] / [COO] × 100 (%) Here, [COO] is the result of saponification by adding excess alcoholic potassium hydroxide solution to the oligomer and back titration with alkaline acid. It is calculated as the number of millimoles of potassium hydroxide consumed per gram of oligomer, and represents the total amount of ester-bonded carboxylic acid residues and free carboxyl groups. [A] is the number of milliequivalents of free carboxyl groups per gram of oligomer determined by neutralization titration in the case of directly esterified oligomers, and the number of milliequivalents of methyl ester terminal groups in the case of transesterified oligomers. The equivalent number is a value measured by a method of quantifying methanol by gas chromatography after hydrolysis. Furthermore, the concentration of glycol end groups was calculated based on the following formula. [OH] = 32.21 - 3.09 [COO] + 0.420 [A] {Here, [OH] represents the number of milliequivalents of glycol end groups per gram of oligomer. } The intrinsic viscosity [η] of the polymer is a value measured at a temperature of 20° C. using an equiweight mixture of phenol and tetrachloroethane as a solvent. The amount of diethylene glycol 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. Regarding the color tone, the obtained polyester was molded into granules and after crystallization at 150°C ± 2°C for 1 hour, the L, a, and b values were determined using a color difference meter. ), the a value represents a red-green hue (+: reddish, -: greenish), and the b value represents a yellow-blue hue (+: yellowish, -: 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. Examples 1 to 8 and Comparative Examples 1 to 4 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 245°C and under normal pressure for a residence time of 6 hours, resulting in a reaction rate of 95.0.
%, [0H] of 2.84 meq., and a DEG% of 1.0% measured in the same manner as for the polymer. Place this oligomer in a glass polymerization tube and
Preliminary polycondensation reaction was carried out at ℃ while changing the time and degree of vacuum. After the reaction, some oligomers were sampled,
This was used as a measurement sample for reaction rate and [OH]. Various aromatic sulfonic acid compounds were added to this reaction mixture in varying amounts, and the pressure was reduced to a final concentration of 0.1 mm.
Table 1 shows the results of polycondensation of Hg at 275°C for a predetermined period of time. According to Table 1, if the reaction rate is less than 96% or if an oligomer with [OH] exceeding 1.5 milliequivalents is used, the DEG% of the polymer will be high and the amount of sulfonic acid compound added will be too small. It can be seen that the polymerization activity is insufficient, and if the amount is too high, the color tone becomes poor and the DEG% increases.

[Table] Example 9 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 220°C to 220°C, and the mixture was heated for 4 hours while distilling methanol. This transesterified oligomer was transferred to a glass polymerization tube and subjected to preliminary polycondensation at 285° C. for 1 hour under reduced pressure. When a part of the product was analyzed, the reaction rate was
99.3%, [OH] was 1.34 meq. After adding 5 x 10 ^-4 mol of benzenesulfonic acid and 2 x 10 ^-4 mol of trimethyl phosphate, the pressure was gradually reduced to 0.1 mmHg and polycondensation was carried out at 275°C for 1.5 hours. The obtained polyester has [η] = 0.68, DEG%
= 2.9, L value = 84.5, a value = -1.6, b value = 2.1. Comparative Example 5 Transesterified oligomer (reaction rate 99.0%, [OH]
Example 9 was carried out under the same conditions as in Example 9, except that the aromatic sulfonic acid and the phosphorus compound were directly added to (3.73 milliequivalent). The obtained polyester has [η] = 0.67, DEG%
= 7.2, L value = 84.1, a value = -1.7, b value = 2.2, which is significantly higher than the polymer obtained in Example 9.
DEG% has become high.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between [OH] of the oligomer and DEG% of the resulting polymer in the case of polycondensation using three types of catalysts.

Claims (1)

[Scope of Claims] 1. Obtained by the reaction of a difunctional carboxylic acid whose main component is terephthalic acid or its ester-forming derivative with a glycol whose main component is ethylene glycol, and whose reaction rate is 96% or more. , and the amount of glycol end groups per gram of oligomer is
Add a sulfonic acid compound represented by the following formula to an oligomer having a weight of 1.5 milliequivalent or less at a rate of 1 x
1. A method for producing polyester, which comprises adding an amount of 10 ^-4 to 10×10 ^-4 equivalent moles and carrying out a polycondensation reaction. Formula (X)- _o A _r (-SO ₃ H) _n m: 1 to 3, n: 0 to 3 A _r : Aromatic group X: OR ₁ , COOR ₂ , halogen However, R ₁ and R ₂ are hydrogen or It is a lower alkyl group. n=0 indicates that there is no nuclear substituent other than the sulfonic acid group. When n≧2, X may be the same or different.