JPH03215522A - Production of polyester - Google Patents

Abstract

PURPOSE:To decrease the amt. of a black contaminant and improve the stability of color tone by polymerizing (a lower-alkyl ester of) an arom. dicarboxylic acid with a glycol in the presence of a polymn. catalyst comprising a specific antimony trioxide. CONSTITUTION:An arom. dicarboxylic acid or a lower-alkyl ester thereof and a glycol are transesterified, and then polycondensed in the presence of a polymn. catalyst comprising antimony trioxide which has a triethylene glycol reductivity of 1.7 or lower, a Bi content of 0.1-100ppm, and an Se content of 1-30ppm.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a polyester that improves and stabilizes the color tone and reduces black foreign matter, and reduces the staining of the spinneret during spinning and film forming. This paper relates to a method for producing polyester. [Prior Art] Polyethylene terephthalate or polyester containing ethylene terephthalate as a main repeating structural unit is extremely valuable in various industrial applications such as fibers and films. Such polyesters are used in various industrial applications,
The characteristics required differ depending on the use. The properties commonly required for both films and fibers are stable color tone, absence of black foreign matter, and little staining of the spinneret during yarn spinning and film production. The color tone can be stabilized by stabilizing the temperature conditions, the degree of vacuum, and the polymerization time during the polycondensation reaction, but fluctuations in the color tone of the volima due to changes in the characteristics of the raw material system, especially the antimony trioxide that serves as the catalyst, are caused by the temperature. This is a situation that must be dealt with by changing conditions such as vacuum. Since changes in temperature and vacuum conditions also affect other qualities of the resulting polyester, it is difficult to stabilize the color tone by changing these conditions. Further, most of the black foreign matter and base stains in the obtained polyester are mainly composed of sb metal. Various methods have been proposed to reduce such black foreign matter, but the reality is that no significant improvement effect has been seen. For example, in JP-A-11-85355, there is an example in which antimony trioxide with a limited Bi content is used, but this has the disadvantage that the polyester used as a catalyst becomes yellowish and the color tone is unstable. [Problem B to be solved by the invention] The purpose of the present invention is to produce yarn with stable color tone and less black foreign matter.
The purpose of this invention is to provide a method for producing polyester that causes less staining of the cap during the film forming process. [Means for Solving the Problems] The object of the present invention is to use reducing triethylene glycol (hereinafter referred to as TEG) as a polymerization catalyst when producing polyester from aromatic dicarboxylic acid or its lower alkyl ester and glycol. is 1.7% or less,
Bi element content 1 is O. IpI)l ~100Dp
m, Se element content is 1 ppm to 30p1)I
This can be achieved by a method for producing polyester characterized by using antimony trioxide, which is n. The TEG reducibility of antimony trioxide in the present invention is evaluated by the following method.

That is, 5 g of antimony trioxide is added to 250 g of TEG, dissolved under stirring at 2506 C to 270 C for 2 hours, and then filtered through filter paper (type 5B) before cooling. After filtration, the filtered material was washed with 100 ml of 6N HCα, and further washed with 100 ml of ethyl alcohol.
dry. The weight of the filtered material was weighed, expressed as a weight percentage relative to the antimony trioxide used, and determined as TEG reducibility. In the present invention, TEG reducibility is 1.7% or less, preferably 1.5% or less, particularly preferably 1.3% or less, and B
The i element content is less than 100 ppm, preferably 70
1) An antimony trioxide catalyst which is less than l) m, particularly preferably less than 50 ppllI, and further has an elemental Se content of 30 pl) m or less, 5 ppm or more, preferably 20 1) I) II or less, 1 oppm or more. using,
If the TEG reducibility exceeds 1.7%, the color tone of the produced polyester will take on an undesirable yellowish tinge. Even if the reducibility of TEG is 1.7% or less, if the Bi element content exceeds 100 1) I) It, the color tone becomes dark and more black foreign matter is generated, which is undesirable. On the other hand, o. If it is less than tppm, the color tone becomes yellowish, which is undesirable. Furthermore, the content of I3i is preferably 1 to 501)I)m. Furthermore, if the content of Se element exceeds 301) l) 01 or less than 11) I) m, the color tone becomes yellowish, which is undesirable. That is, the reducibility of TEG and the I
The polyester targeted by the present invention can only be produced by using antimony trioxide as a catalyst that satisfies the three requirements of 3i element content and Se content.

As the method for producing the polyester of the present invention, conventionally known methods can be employed. For example, a method in which a lower alkyl ester of terephthalic acid such as dimethyl terephthalate and ethylene glycol are used as raw materials to perform a transesterification reaction and then polycondensation, or a method in which terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG) is Either method may be applied, including esterification reaction as a raw material and then polycondensation. Further, the method for producing polyester may be a batch method, a continuous method, or a semi-continuous method using a partially continuous method.

Antimony trioxide is added before the start of the polycondensation reaction, but it can also be added to the reaction system before the start of the transesterification or esterification reaction. Also, the method of adding antimony dioxide is powder form, (EG)
It may be either a slurry of (EG) or a solution dissolved in (EG), and there are no particular limitations. The polyester produced by the present invention is preferably a polyester produced from an aromatic carboxylic acid or its lower alkyl ester and glycol, but it is preferable to use a polyester produced by adding or copolymerizing a dibasic acid such as isophthalic acid, phthalic acid, or diethylene glycol or a polyhydric alcohol. May be polyester. Depending on the purpose, inert inorganic particles such as calcium carbonate, silica, titanium oxide, etc. may be added during the manufacturing process, or particles precipitated by the reaction of compounds added during the polyester manufacturing process, so-called internal particles, may be included. Also, when manufacturing polyester,
Known modifiers and stabilizers that are usually added can be blended.

[Examples] The present invention will now be explained in more detail with reference to Examples. In addition, parts in the examples represent parts by weight. In addition, each measurement value in the examples was determined by the following method. A. It was determined by atomic absorption spectrometry for stars containing bismuth elements in antimony trioxide. B. Selenium element content in antimony oxide was determined by ICP method. C. Intrinsic viscosity was measured at 25°C using 0-chlorophenol as a solvent. D. The black foreign matter polyester was formed into a biaxially stretched film with a thickness of 0.1 m, which was enlarged using a stereomicroscope and visually observed to express the number of foreign matter per 1 g of film. E. Polyester color tone Chip-shaped polyester is processed using a color machine (Suga Test Machine).
Co., Ltd.) and expressed as L and b values. Example I A bis-β-hydroxylethyl terephthalate low polymer (hereinafter referred to as B I-I T) obtained by esterifying 85.8 parts of TPA and 38.5 parts of EG at 260°C for 4 hours was treated with TEG reducibility. 1.10%, Bi element content 4
81) Adding 0.025 part of antimony trioxide containing pm, Se element Jt 13 ppm, 0.06 part of trimethyl phosphate, and 0.12 part of calcium acetate,
A polycondensation reaction was carried out at 290"C under a reduced pressure of 0.5 mnHg for 3 hours and 10 minutes. The obtained polymer had a b value of 5.0,
The L value was 41.0, the intrinsic viscosity was 0.650, and the amount of black foreign matter was 0/g. When this polymer was spun, good polyester yarn was obtained with almost no staining on the spindle. Example 2 In Example 1, antimony trioxide to be added is TEG
Reducibility 0.95%, Bi element content 25 ppm, Se element content jE2 0! )I) It was carried out in the same manner as in Example 1, except that In was used. The obtained polyester had a b value of 5.2, an L value of 41.5, an intrinsic viscosity of 0.618, and a black foreign material content of 1 piece/g. As a result of forming a film using this polymer, there was little fouling of the die and the film forming properties were good. Example 3 100 parts of dimethyl terephthalate, 70 parts of (EG), 0.07 part of calcium acetate and 1.20% TEG reducibility, B
I element content jtl 5 ppm, Se element content 17 ppm
After adding antimony dioxide and carrying out a transesterification reaction according to a conventional method, 0.015 part of phosphorous acid was added and excess (EG) was distilled off to obtain bis-β-hydroxyethyl terephthalate. The polyester obtained by polycondensing this for 2 hours and 5 minutes according to a conventional method had an intrinsic viscosity of 0.615, a b value of 5.1, an L value of 40.8, and had 0 black foreign matter/g. When this polyester was yarn-spun, the yarn-spinning properties were good and there was no staining of the spinneret. Example 4 The same method as Example 3 was carried out except that the antimony trioxide shown in Table 1 was used. The properties of the obtained polyester were of good quality as listed in Table 1. Comparative Example 1 In Example 1, as antimony dioxide, TEG reducibility 0.95%, Bi element content, 180 pl) lns
It was carried out in the same manner as in Example 1, except that antimony trioxide with an e-element content of 7 ppm was used. The obtained polyester was dark in color and contained many black foreign substances.

(Table 1,) Comparative Examples 2 and 3 The same method as in Example 1 was carried out except that antimony trioxide in Table 1 was used. As shown in Table 1, the obtained polyester had a yellowish color tone and contained many black foreign substances. Comparative Examples 4 to 7 Comparative examples 4 to 7 were conducted in the same manner as in Example 3, except that antimony trioxide shown in Table 1 was used. In both cases, the polyester obtained was of poor quality. (Hereinafter in the margin) [Effects of the Invention] The method for producing polyester of the present invention is a suitable method for obtaining polyester that has good and stable color tone and has few black foreign substances. Further, when the obtained polyester is applied to a yarn spinning or film forming process, a product with less staining of the spinneret and a stable color tone can be obtained.

Claims (1)

[Claims] When producing polyester from aromatic dicarboxylic acid or its lower alkyl ester and glycol, triethylene glycol reducibility is 1.7% as a polymerization catalyst.
Below, the content of Bi element is 0.1 ppm to 100 ppm
, a method for producing polyester, characterized in that antimony trioxide having a Se element content of 1 ppm to 30 ppm is used.