JPH0449850B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing polyester, particularly a method for producing a highly polymerized polyester having good transparency, color tone, and excellent thermal properties in a short time. (Prior Art) Polyesters, particularly polyethylene terephthalate or polyesters having ethylene terephthalate units as their main constituent units, have excellent properties and have therefore been widely used in fibers, films, and other molded products. To produce polyethylene terephthalate, bis-(β-hydroxyethyl) is usually produced by transesterifying dimethyl terephthalate and ethylene glycol or directly esterifying terephthalic acid and ethylene glycol
It is produced by forming terephthalate or a low polymer thereof and then subjecting it to a polycondensation reaction to obtain a polyester with desired properties. However, the polycondensation process, especially the final polycondensation process, is usually carried out at 280°C for a long time.
Because high temperatures of between 300 and 300 degrees Celsius are required, for example, in order to obtain polyester with an intrinsic viscosity of 0.6 or higher, there are almost always thermal decomposition reactions and other side reactions involved, which usually result in yellow coloring or The physical properties of the polyester will be impaired due to an increase in the content of diethylene glycol bonds. Catalysts are generally used in the production of polyesters, and aromatic sulfonic acid compounds are known as catalysts that provide polyesters with good transparency and color tone (Japanese Patent Application Laid-open No. 157625/1983). However, compared to germanium compounds and antimony compounds, which are typical polycondensation catalysts, aromatic sulfonic acid compounds and other sulfuric acid compounds are more likely to be present in diethylene glycol (hereinafter referred to as "diethylene glycol") in the resulting polymer.
The drawback is that the amount of the component (referred to as DEG) is large and the softening point of the polymer is low. In addition, the catalytic activity is slightly inferior, and when polycondensation is carried out for a long time in order to obtain a polyester with a high degree of polymerization, attention is paid to the yellow color of the polyester. (Problems to be Solved by the Invention) The present invention improves the method of producing polyester using a sulfur acid compound as a catalyst, and produces a highly polymerized polyester with good transparency, color tone, and excellent thermal properties in a short time. The purpose is to provide a method for manufacturing. (Means for Solving the Problems) In order to achieve the above-mentioned object, the present inventors have conducted intensive research and found that if an ester oligomer or prepolymer is depolymerized with a small amount of water, then a sulfur acid compound is added. The present invention was achieved by discovering that a high polymerization degree polymer with a small amount of DEG produced can be obtained in a short period of time. That is, the gist of the present invention is as follows. When producing polyester by polycondensing bis(β-hydroxyethyl) terephthalate or its low polymer, an ester oligomer or prepolymer having an intrinsic viscosity of 0.06 to 0.40 is added at 1×10 ^-4 per mole of the acid component constituting the polyester. ~500× ^10-4
After depolymerizing with mol of water, the sulfuric acid compound is added to 0.1×
A method for producing polyester, which comprises adding 10 ^-4 to 100×10 ^-4 equivalents to complete polycondensation. Bis(β-hydroxyethyl) in the present invention
Terephthalate or its low polymer (abbreviated as BHET) can be obtained by subjecting terephthalic acid or its ester-forming derivative to esterification reaction or transesterification reaction with ethylene glycol. For example, terephthalic acid and ethylene glycol are mixed in the presence of BHET at 230~
The esterification reaction may be carried out at 270°C. In the present invention, an ester oligomer or prepolymer having an intrinsic viscosity of 0.06 to 0.40 produced without a catalyst or in the presence of a relatively small amount of a polycondensation catalyst is depolymerized with water, and at this time, the amount of water added is adjusted to the amount constituting the polyester. 1×10 ^-4 to 500× per mole of acid component
10 ^-4 mol, preferably 20 x 10 ^-4 to 200 x 10 ^-4
It is a mole. If it is less than 1×10 ^{−4 mol} , depolymerization will not substantially occur, and if it exceeds 500×10 ⁻⁴ mol, the reaction system will stick when water is added, which is not preferable. In addition, if the intrinsic viscosity is less than 0.06, DEG
If there is no effect of suppressing the amount of components and the intrinsic viscosity exceeds 0.40, not only will the effect be saturated, but it will take a long time to increase the intrinsic viscosity, which is unfavorable from the viewpoint of polymer coloration and productivity. Depolymerization is preferably carried out in a closed system for 30 to 60 minutes. Further, after the depolymerization, a sulfur acid compound is added as a catalyst, and the amount of the sulfur compound added at this time needs to be 0.1×10 ⁻⁴ to 100×10 ⁻⁴ equivalent per mole of acid component. The optimal amount of the sulfuric acid compound to be added varies depending on the type of compound; for example, for aromatic sulfonic acids substituted with carboxyl groups or halogens, it is 0.1×10 ^-4 ~
10 ^-4 equivalent/mole of acid component, 10 x 10 ^-4 to 100 x 10 ^-4 equivalent/mol for aliphatic sulfonic acid and benzyl sulfonic acid
It becomes the acid component mole. If the amount of the sulfuric acid compound added is less than this range, polycondensation will take a long time, and if it exceeds this range, not only will the polyester be colored yellow, but the content of DEG bonds will increase. Sulfur acid compounds (including acid anhydrides) used in the present invention include sulfur, acetyl sulfate,
Sulfuric acid esters (e.g. dimethyl sulfate, diethyl sulfate, ethyl hydrogen sulfate, isopropyl hydrogen sulfate, dodecyl hydrogen sulfate, octadecyl hydrogen sulfate, phenyl hydrogen sulfate), aliphatic sulfonic acids and their derivatives (e.g. methanesulfonic acid, trifluoromethanesulfonic acid, ethane Sulfonic acid, ethyl ethanesulfonate, methanesulfonyl chloride, methanedisulfonic acid, 2-hydroxy-1-ethanesulfonic acid, 3-hydroxy-1-propanesulfonic acid, propanesultone, sulfoacetic acid, 2-amino-1-ethane sulfonic acid), aromatic sulfonic acids and their derivatives (e.g. benzenesulfonic acid, p-
Toluenesulfonic acid, 3,4-dimethylbenzenesulfonic acid, p-benzenesulfonic acid, 1,3,
5-benzenetrisulfonic acid, p-chlorobenzenesulfonic acid, m-nitrobenzenesulfonic acid,
4-chloro-3-methyl-5-nitrobenzenesulfonic acid, hydroxybenzenesulfonic acid, o-
Formylbenzenesulfonic acid, o-aminobenzenesulfonic acid, methyl benzenesulfonate, benzenesulfonyl chloride, benzenesulfonamide, o-sulfobenzoic acid, o-sulfobenzoic anhydride, 4-sulfoisophthalic acid, 5-sulfosalicylic acid, naphthalenesulfonic acid, 1,8-naphthalenesultone, 1,8-naphthalenesultam, anthracenesulfonic acid, benzoquinonesulfonic acid, naphthoquinonesulfonic acid), anthraquinonesulfonic acid), alicyclic sulfonic acids (e.g. cyclopentanesulfonic acid, cyclohexane sulfonic acids), aralkyl sulfonic acids (e.g. phenylmethane sulfonic acid, α-phenylethanesulfonic acid), heterocyclic sulfonic acids (e.g. pyridine sulfonic acid, thiazole sulfonic acid, imidazole sulfonic acid, furan sulfonic acid, pyrrole sulfonic acid) , non-benzene aromatic sulfonic acids (eg, tropolone sulfonic acid, azulene sulfonic acid), natural or synthetic polymeric sulfonic acids (eg, lignin sulfonic acid, polyvinyl sulfonic acid, polystyrene sulfonic acid, sulfonated polyacrylic acid), and the like. Note that if these sulfuric acid compounds have a free acidic group, they may be in the form of ammonium salts (including alkyl or arylammonium salts) or esters, but they may be in the form of alkali metal salts or alkaline earth metal salts. Salts have no polymerization activity and are unsuitable. 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, trimellitic acid, propylene glycol, 1,4-cyclohexanedimethanol, pentaerythritol, etc. as copolymer components. In some cases, a matting agent such as titanium dioxide may be added to produce a matte polyester. (Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way. In the examples, characteristic values were measured as follows. (a) Intrinsic viscosity The ester oligomer or polyester was dissolved in a mixed solvent of equal weights of phenol and tetrachloroethane, and the intrinsic viscosity was measured at 20°C. (b) Content of DEG bonds After polyester was hydrolyzed with alkali, ethylene glycol and DEG were determined by gas chromatography.
Quantify the mol% of DEG to total glycol
(denoted as DEG%). (c) Color tone The obtained polyester was molded into granules and heated at 150℃.
After crystallization at ±2℃ for 1 hour, L,
The a and b values were determined. 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. Examples 1 to 5 and Comparative Examples 1 to 4 A slurry of terephthalic acid and ethylene glycol (ethylene glycol/terephthalic acid molar ratio 1.2) was continuously supplied to an esterification reactor in which BHET was present, and the temperature was 250°C. The esterification reaction was carried out under reduced pressure for a residence time of 5 hours and 15 minutes, and a direct esterification product with an esterification reaction rate of 95%, [η] 0.10, and DEG% 1.1 was continuously obtained. This product was placed in a stainless steel test polymerization apparatus, water was added in the amount shown in Table 1, and the product was placed in a closed system.
After depolymerizing at 275°C for the time shown in Table 1, the amount of sulfuric acid compound shown in Table 1 was added, and at a temperature of 275°C 0.1
Polycondensation was carried out under reduced pressure of mmHg for 3 hours. The results shown in Table 1 were obtained. According to Table 1, when the amount of water added is less than 1 x 10 ^-4 mol per mol of the acid component constituting the polyester, the DEG% increases significantly and the color tone deteriorates (the b value increases). On the other hand, if it exceeds 500×10 ^-4 mol, the polyester will stick, and it will take more than one hour for the stuck polyester to melt, and furthermore, the [η] of the final polyester will not increase and the color tone will deteriorate. Furthermore, if the amount of the sulfonic acid compound added is less than 0.1 x 10 ^-4 mol per mol of the acid component constituting the polyester, not only will the [η] of the final polyester not reach the target, but the color tone will deteriorate significantly; If it exceeds 100×10 ^-4 mol, the color tone of the final polyester will deteriorate and the DEG% will also increase.

[Table] The amount of water and sulfonic acid compound added is per mole of the acid component constituting the polyester, and the unit is
10 ^-4 mol. In the table, OSB: o-sulfobenzoic anhydride SS: sulfosalicylic acid BS: benzenesulfonic acid SA: sulfuric acid CB: chlorobenzenesulfonic acid. Example 6 Antimony trioxide was added to the direct esterification product obtained in Example 1 in an amount of 1 x 10 ^-4 mol/mol of acid component and polycondensed for 2 hours to obtain a polyester prepolymer with [η] = 0.38. I got it. After adding 50×10 ^-4 mol/mol of acid component of water and depolymerizing in a closed system for 2 hours, 4-sulfophthalic acid was added in an amount of 1.0×10 ^-4 mol/mol of acid component. Time polycondensation was carried out. The obtained polyester was [η] = 0.72, DEG%
= 1.96, L value = 84.0, a value = -1.3, b value = 1.9, and the color tone and transparency were good. For reference, the amount of antimony trioxide added is 2x
The same procedure as in Example 6 was carried out except that the setting was 10 ^-4 mol/mol of acid component and 4-sulfophthalic acid was not added, and the obtained polyester had [η]=0.71,
DEG% = 1.77, L value = 72.2, a value = -2.6, b value =
1.8, and it was a slightly dark, dull, greenish polymer. (Effects of the Invention) According to the method of the present invention, the polycondensation time is shortened, the by-product of DEG bonds is suppressed, and transparency and
It becomes possible to industrially advantageously produce high-quality polyester with good color tone and good thermal properties.

Claims (1)

[Claims] 1. When polycondensing bis(β-hydroxyethyl) terephthalate or its low polymer to produce polyester, an ester oligomer or prepolymer having an intrinsic viscosity of 0.06 to 0.40 is added at 1×10 ^{− 4} ~500×
After depolymerization with 10 ^-4 mol of water, the sulfuric acid compound is
0.1 per mole of acid component constituting polyester
A method for producing polyester, which comprises adding x10 ^-4 to 100 x 10 ^-4 equivalents to complete polycondensation.