JP2000146940A - Method for determining amount of diethyleneglycol in polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily measure a fine diethylglycol content in polyester by thermally decomposing polyester under the coexistence of an organic alkali reagent and using thermal decomposition gas chromatography for the obtained product. SOLUTION: An organic alkali reagent is added to polyester, hydrolysis and formation of methylderivative are made simultaneously by a thermal decomposition device, and a solution of tetramethylammoniumhydrooxide is used for the organic alkali reagent. A vertical heating oven type thermal decomposition device is used for thermal decomposition and temperature near a room temperature is maintained up to a point immediately before a sample holder is exposed to thermal decomposition, thus minimizing sample loss. An optimum thermal decomposition temperature is approximately 400 deg.C. When polyester is in a granular form, it is pulverized to increase the contact area with a reagent, thus performing thermal decomposition and the formation of methylderivative smoothly and hence improving measurement accuracy. Therefore, a small amount of diethyleneglycol content that is contained as the polymerization by-product of polyester can be measured by conventional thermal decomposition chromatography.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for measuring the content of diethylene glycol in a polyester.

[0002]

2. Description of the Related Art Diethylene glycol, which is present in minute amounts in the molecular chain as a by-product during the production of polyesters such as polyethylene terephthalate, adversely affects the mechanical and thermal properties of polyesters. It is important to understand its content to prevent it.

[0003] With respect to the amount of diethylene glycol contained in the polyester-based polymer, it is widely known to determine the diethylene glycol content by chemically decomposing the polyester by hydrolysis, hydrazine decomposition, or the like, and analyzing the decomposition products by gas chromatography. Have been. If the polyester is soluble in a solvent, the polyester solution can be quantified by liquid high-resolution ¹ H-NMR.

[0004] However, the above-mentioned quantitative analysis of the composition by the chemical decomposition-gas chromatography method has disadvantages that the analysis time is long and the operation is complicated. Further, quantification by liquid high-resolution ¹ H-NMR has the disadvantage that the apparatus is expensive and the range of application is limited to those soluble in solvents.

[0005]

Accordingly, the present invention provides
It is an object of the present invention to provide a method for easily and simply measuring a small amount of diethylene glycol in a polyester without using an expensive apparatus such as liquid high-resolution ¹ H-NMR.

[0006]

SUMMARY OF THE INVENTION The present invention resides in a method for measuring the content of diethylene glycol in a polyester by using pyrolysis gas chromatography of a product obtained by pyrolyzing a polyester in the presence of an organic alkali reagent.

Further, the present invention relates to a method for measuring the content of diethylene glycol in the above-mentioned polyester, wherein the polyester is a polymer containing ethylene glycol as a constituent component and the content of diethylene glycol contained as a by-product in the polymerization in a trace amount. .

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Pyrolysis gas chromatography used in the present invention has been conventionally used as a method for measuring the copolymer composition of various polymers such as polyesters and other condensation polymers. For example, regarding the method for analyzing the copolymer composition of liquid crystal polyester, (1) H. Ohtani,
R. Fujii, S. Tsuuge: J. High Res. Chromatogr., 14, 388 (199
Introduced by 1).

Further, regarding the method of analyzing the copolymer composition of polycarbonate, (2) Y. Ito, H. Ogasawara, Y. Ishida, H. Ohtan
i, S.Tsuge: Polym.J., 28,1090 (1996) and (3) Y.Ishida,
S.Kawaguchi, Y.Ito, H.Ohtani, S.Tsuge: J.Anal.Appl.Pyr
olysis, 40-41, 321 (1997).

The present invention further develops the above-mentioned measuring method for measuring the copolymer composition of various polymers such as polyesters and other condensation polymers, and thereby makes it possible to minimize the amount of traces contained as by-products of polymerization in polyesters. The present invention provides a novel method for measuring the diethylene glycol content of water.

In the present invention, hydrolysis and methyl derivatization are simultaneously carried out in a pyrolyzer by adding an organic alkali reagent to the polyester. The organic alkali reagent used at this time is a solution of tetramethylammonium hydroxide, especially In order to efficiently decompose the decomposition product of the compound into a methyl derivative, a methanol solution thereof is desirable.

The pyrolysis apparatus used is a vertical heating furnace type pyrolysis that maintains the temperature near room temperature until just before the sample holder is exposed to the pyrolysis temperature and minimizes loss of reagents due to vaporization and decomposition. A device is desirable. Further, since a liquid organic alkali reagent is used, a cup-shaped reagent holder from which the reagent hardly flows out is desirable.

If the thermal decomposition temperature is too high, the organic alkali reagent is instantaneously decomposed, so that hydrolysis of the polyester and derivatization of the decomposition product with methyl are not performed efficiently, and a side reaction due to heat is likely to occur. Therefore, it is desirable that the temperature be as low as possible. However, when the temperature is 200 ° C. or lower, the volatility of the product is low, so that introduction into the gas chromatograph does not occur instantaneously, and the peak is tailed.

As a result of various studies, the thermal decomposition temperature was set to 300 ° C.
It has been confirmed that the above measurement is possible at ~ 600 ° C, but the optimal temperature is around 400 ° C. The polyester may be in a granular state, but in that case, it is desirable to pulverize as much as possible to increase the contact area with the organic alkali reagent. Furthermore, in the case of a polyester soluble in a solvent, the amount of the sample can be made constant by dissolving it in a solvent such as hexafluoroisopropanol and then volatilizing the solvent after putting it in a sample holder with a microsyringe or the like, and By forming the thin film, the contact area with the organic alkali reagent can be increased, and the thermal decomposition and the methyl derivatization of the decomposition product can be performed smoothly, so that the measurement accuracy can be improved.

[0015]

〔Measurement condition〕

Thermal decomposition temperature: 400 ° C. Supply reagent amount: 50 μg (2 μl of a 25 mg / ml hexafluoroisopropanol solution) Organic alkaline reagent: 4 μl of a 25% methanol solution of tetramethylammonium hydroxide Injection temperature: 300 ° C. Detection unit temperature: 300 ° C. Column oven heating temperature: Hold at 35 ° C for 5 minutes,
The temperature is raised at a rate of 5 ° C./min and maintained at 280 ° C. for 6 minutes. Separation column: DB-1701 manufactured by J & W (30m × 0.
25 mm D. Carrier gas: He 1 ml / min (constant flow rate control) Split ratio: 1/40 Gas chromatography detector: FID

Example 1 A pyrogram obtained by pyrolysis gas chromatography of a product obtained by pyrolyzing a polyester containing ethylene glycol having the composition shown in Table 1 as a constituent in the presence of an organic alkali reagent. Figure 1
It was shown to. The peak area ratio of diethylene glycol to ethylene glycol was measured. The results are shown in Table 2 together with the molar ratio of diethylene glycol to ethylene glycol determined by liquid high resolution ¹ H-NMR.

[0017]

[Table 1]

[0018]

[Table 2]

The peak area of diethylene glycol to ethylene glycol determined by pyrolysis gas chromatography in the presence of an organic alkali reagent is plotted on the horizontal axis with the molar ratio between diethylene glycol and ethylene glycol determined by liquid high-resolution ¹ H-NMR in Table 2. FIG. 2 shows a calibration curve prepared by taking the ratio on the vertical axis.

As shown in FIG. 2, liquid high resolution ¹ H-N
The molar ratio of diethylene glycol to ethylene glycol by MR is plotted on the horizontal axis, and the peak area ratio of diethylene glycol to ethylene glycol by pyrolysis gas chromatography in the presence of an organic alkali reagent is represented by R
² = 0.9988, which is a good linear relationship, and the regression equation y
= 1.1233x-0.0034. Here, x and y in the regression equation are as follows: x is the molar ratio of diethylene glycol to ethylene glycol (liquid high resolution ¹ H-NM
R) and y is the peak area ratio of diethylene glycol to ethylene glycol (determined from pyrolysis gas chromatography in the presence of an organic alkali reagent).

Therefore, when an unknown sample is analyzed by pyrolysis gas chromatography, the ratio of the peak areas of ethylene glycol and diethylene glycol comes out, and it is substituted for y in the regression equation to obtain x (molar ratio). I will ask. P
Since the composition ratio (mol) of ethylene glycol in ET is known at the stage of preparation, the composition ratio (mol) of diethylene glycol in PET can be calculated. .

Comparative Example 1 The diethylene glycol content of a polyester containing ethylene glycol having the composition shown in Tables 1 and 3 was measured by hydrazinolysis-gas chromatography. Table 4 shows the results.

[0023]

[Table 3]

Example 2 The peak area ratio of diethylene glycol to ethylene glycol was measured by pyrolysis gas chromatography of the same sample as in Comparative Example 1 under the same conditions as in Example 1 in the presence of an organic alkali reagent. From the regression equation determined in Example 1, the molar ratio of diethylene glycol to ethylene glycol was determined. Further, the diethylene glycol content was obtained from the obtained molar ratio and the charged composition. Table 4 shows the results.

As shown in Table 4, the content of diethylene glycol determined by pyrolysis gas chromatography in the presence of an organic alkali reagent is the same as the value determined by hydrazine decomposition-gas chromatography.
It turns out that the analysis value is reliable and accurate. In addition, while the measurement time of hydrazine decomposition-gas chromatography was required day and night, pyrolysis gas chromatography in the coexistence of an organic alkali reagent was as short as about 2 hours.

[0026]

[Table 4]

[0027]

As described above, the method of the present invention makes it possible to measure the content of a trace amount of diethylene glycol present as a by-product of polymerization in a polyester containing ethylene glycol as a component in a short time and easily, and to control the quality of the product. It promotes the efficiency of manufacturing.

[Brief description of the drawings]

FIG. 1 is a pyrogram obtained by pyrolysis gas chromatography of a sample A in Example 1 in the presence of an organic alkali reagent.

FIG. 2 is a graph showing the relationship between the molar ratio of diethylene glycol to ethylene glycol by liquid high-resolution ¹ H-NMR and the peak area ratio of diethylene glycol to ethylene glycol by pyrolysis gas chromatography in the presence of an organic alkali reagent.

Claims (5)

[Claims] 1. A diethylene glycol content in a polyester obtained by pyrolyzing a polyester in the coexistence of an organic alkali reagent and measuring the diethylene glycol content in the polyester by pyrolysis gas chromatography. Measurement method. 2. The method according to claim 1, wherein a polymer containing ethylene glycol as a constituent component of the polyester and containing a small amount of diethylene glycol as a by-product of polymerization is used. 3. The method for quantifying the amount of diethylene glycol in a polyester according to claim 1, wherein tetramethylammonium hydroxide is used as the organic alkali reagent. 4. A polyester having a thermal decomposition temperature of 300 to 300.
4. The method according to claim 3, wherein a temperature of 600 [deg.] C. is used. 5. The method for quantifying the amount of diethylene glycol in a polyester according to claim 1, wherein the amount of the diethylene glycol component is quantified by converting the diethylene glycol component generated by thermal decomposition of the polyester into a methyl derivative.