JP2017219517A - Method of estimating number-average molecular weight and maximum stress of thermoplastic polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of estimating number-average molecular weight and maximum stress of a thermoplastic polyester sample without making a GPC measurement.SOLUTION: A method of estimating number-average molecular weight of a thermoplastic polyester sample comprises the steps of; (a) preparing a thermoplastic polyester; (b) degrading the thermoplastic polyester; and (c) measuringH-NMR of undegraded and degraded samples, deriving terminal amounts of the undegraded and degraded samples, and an ester structure decomposition amount and ether structure decomposition amount of the degraded sample in terms of mol% (N-value) with respect to entire constituting units of the thermoplastic polyester using an expression: N=[(a terminal amount of the undegraded sample)×1/2]+(an ester structure decomposition amount of the degraded sample)+(an ether structure decomposition amount of the degraded sample), and deriving a number-average molecular weight (Mn) using an expression: Mn=[(formula weight of a composition formula of the thermoplastic polyester)×100]/N.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for estimating molecular weight and maximum stress in a deteriorated sample of thermoplastic polyester.

  Thermoplastic polyester is a material having flexibility and toughness, and is widely used for films, packaging materials, textile fibers, and the like. When the thermoplastic polyester material deteriorates due to the influence of ultraviolet rays, rain, temperature, humidity, etc., the maximum stress, which is a characteristic of the material, decreases. It is known that the progress of molecular chain breakage by ultraviolet rays or water contributes to this, and it is known that the maximum stress decreases when the molecular weight is below the limit molecular weight. Therefore, in evaluating a deteriorated material, a molecular weight distribution is generally measured by a tensile test and gel permeation chromatography (GPC) (Non-patent Document 1). If the correlation between the maximum stress and the molecular weight is known, it is possible to estimate the maximum stress from the results of molecular weight measurement. The tensile test tends to vary in test results and is a destructive test. Therefore, many test pieces need to be prepared, and the amount of work can be reduced if the maximum stress can be estimated only by molecular weight measurement. However, the molecular weight distribution is measured by GPC, for example, when measuring polyethylene terephthalate (PET), which is a representative example of thermoplastic polyester material, 1,1,1,3,3,3- There is a problem that it is necessary to use several liters of hexafluoro-2-isopropanol. Therefore, a measurement method using a mixed solvent of 1,1,1,3,3,3-hexafluoro-2-isopropanol and chloroform has been reported (Non-Patent Document 2), but the high running cost has been solved. Not.

W. Wang, A. Taniguchi and T. Okada etc., J. Appl. Polym. Sci., 1998, 67, 705-714. Kuwahiro Kuwahara and Kazuaki Noda, Research on paints, No. 150, October, p9-15, 2008. A. M. Ilarduya and S. M. Guerra, Macromol. Chem. Physics, 2014, 215, 2138-2160. M. Day, D. M. Wiles, J. Appl. Polym. Sci., 1972, 16, 191-202.

  An object of the present invention is to provide a technique for estimating the number average molecular weight and the maximum stress of a thermoplastic polyester deteriorated sample without performing GPC measurement.

In the present invention, a sample of a thermoplastic polyester and a sample in which the thermoplastic polyester is deteriorated (preferably, a sample deteriorated by an accelerated weathering test) are prepared, and by ¹ H-NMR (proton nuclear magnetic resonance) measurement, By quantifying the terminal amount of the undegraded and degraded thermoplastic polyester sample, the degradation amount of the ester structure of the degraded thermoplastic polyester, and the degradation amount of the ether structure of the degraded thermoplastic polyester, the thermoplasticity can be measured without performing GPC measurement. The present invention relates to a method for estimating the number average molecular weight and maximum stress of polyester.

  The first of the present invention is a method for estimating the number average molecular weight of a thermoplastic polyester. This method includes the following steps.

(A) preparing a sample of thermoplastic polyester;
(B) deteriorating the thermoplastic polyester to obtain a deteriorated thermoplastic polyester;
(C) The ¹ H-NMR spectrum of undegraded thermoplastic polyester (undegraded thermoplastic polyester) and degraded thermoplastic polyester is measured, and the terminal amounts of undegraded thermoplastic polyester and degraded thermoplastic polyester, degraded thermoplastic polyester The amount of decomposition of the ester structure and the amount of decomposition of the ether structure of the deteriorated thermoplastic polyester are calculated from the following formula (Formula 1) as mol% (N) with respect to all the structural units of the thermoplastic polyester,
N = [(terminal amount of undegraded thermoplastic polyester) × 1/2] + (decomposition amount of ester structure of deteriorated thermoplastic polyester) + (decomposition amount of ether structure of deteriorated thermoplastic polyester) (Formula 1)
Step of obtaining number average molecular weight (Mn) from the following formula (Formula 2): Mn = [(Formula weight of composition formula of thermoplastic polyester) × 100] / N (Formula 2).

  The second of the present invention is a method for estimating the maximum stress of the thermoplastic polyester. This method includes the following steps.

(A) preparing a sample of thermoplastic polyester;
(B) deteriorating the thermoplastic polyester to obtain a deteriorated thermoplastic polyester;
(C) The ¹ H-NMR spectrum of undegraded thermoplastic polyester (undegraded thermoplastic polyester) and degraded thermoplastic polyester is measured, and the terminal amounts of undegraded thermoplastic polyester and degraded thermoplastic polyester, degraded thermoplastic polyester A step of calculating the decomposition amount of the ester structure and the decomposition amount of the ether structure of the deteriorated thermoplastic polyester as a mol% (N) with respect to all the structural units of the thermoplastic polyester, from the following formula (Formula 1):
N = [(terminal amount of undegraded thermoplastic polyester) × 1/2] + (decomposition amount of ester structure of deteriorated thermoplastic polyester) + (decomposition amount of ether structure of deteriorated thermoplastic polyester) (Formula 1)
(D) measuring the tensile strength of the undegraded thermoplastic polyester and the degraded thermoplastic polyester, and obtaining a correlation between the value of N and the tensile strength;
(E) Prepare an unknown sample of the thermoplastic polyester whose maximum stress is to be measured, calculate N of the unknown sample according to steps (b) and (c), and calculate the maximum stress of the unknown sample from the correlation of step (d) The process of estimating.

In the first invention and the second invention, it is preferable that the thermoplastic polyester is deteriorated by an accelerated weather resistance test in the step (b). In the first and second inventions, the degradation amount of the ester structure of the deteriorated thermoplastic polyester is defined as an increase in the amount of aromatic carboxylic acid terminals in the ¹ H-NMR spectrum of the deteriorated thermoplastic polyester. The amount of decomposition of the ether structure of the thermoplastic polyester is preferably quantified as the amount of decrease in the ether structure of the ¹ H-NMR spectrum of the deteriorated thermoplastic polyester.

  According to the present invention, it is possible to estimate the number average molecular weight and maximum stress of a thermoplastic polyester without performing GPC measurement.

It is a graph which shows the correlation with N value computed from < ¹ > H-NMR, and the measured maximum stress. It is a conceptual diagram for estimating the value of the maximum stress of an unknown sample from the graph which shows the correlation with N value computed from < ¹ > H-NMR of an unknown sample, N value of FIG. 1, and the measured maximum stress. 2 is an example of ¹ H-NMR spectrum of a PET sample measured in Example 1. FIG. FIG. 4 is a partially enlarged view of FIG. 3. It is a graph which shows the correlation with the N value computed from < ¹ > H-NMR, and the number average molecular weight measured by GPC. It is a graph which shows the correlation with the N 'value computed from < ¹ > H-NMR when not taking the decomposition | disassembly of the polyester which has an ether structure into consideration, and the number average molecular weight measured by GPC. It is a graph which shows the correlation of N value of Example 2, and maximum stress. It is a graph which shows the correlation with the N 'value calculated from < ¹ > H-NMR when not taking the decomposition | disassembly of polyester which has an ether structure into consideration, and the measured maximum stress.

  The present invention will be described below. In the present specification, undegraded thermoplastic polyester refers to a thermoplastic polyester before performing a degradation test including an unknown sample for which a number average molecular weight or maximum stress is desired, preferably an accelerated weather resistance test. The term “undegraded thermoplastic polyester” refers to a material that has been deteriorated by a deterioration test, preferably an accelerated weather resistance test.

  The first of the present invention is a method for estimating the number average molecular weight of a thermoplastic polyester. This method includes the following steps.

(A) preparing a sample of thermoplastic polyester;
(B) deteriorating the thermoplastic polyester to obtain a deteriorated thermoplastic polyester;
(C) The ¹ H-NMR spectrum of undegraded thermoplastic polyester (undegraded thermoplastic polyester) and degraded thermoplastic polyester is measured, and the terminal amounts of undegraded thermoplastic polyester and degraded thermoplastic polyester, degraded thermoplastic polyester The amount of decomposition of the ester structure and the amount of decomposition of the ether structure of the deteriorated thermoplastic polyester are calculated from the following formula (Formula 1) as mol% (N) with respect to all the structural units of the thermoplastic polyester,
N = [(terminal amount of undegraded thermoplastic polyester) × 1/2] + (ester structure decomposition amount of deteriorated thermoplastic polyester) + (ether structure decomposition amount of deteriorated thermoplastic polyester) (Formula 1)
Step of obtaining number average molecular weight (Mn) from the following formula (Formula 2): Mn = [(Formula weight of composition formula of thermoplastic polyester) × 100] / N (Formula 2).

  In step (a), a sample of thermoplastic polyester is prepared. Examples of the thermoplastic polyester that can be used in the method of the present invention include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT). A sample is prepared by cutting the thermoplastic polyester into test pieces of a predetermined size. Although the magnitude | size of a test piece is not specifically limited, It is set as a magnitude | size large enough to perform the accelerated weathering test and tension test which are mentioned later. For example, in the case of a PET sample, a size such as 15 cm × 7.5 cm × 0.5 mm can be exemplified. Moreover, you may use the test piece punched in the shape of the type | mold used by a tension test.

In the following description, polyethylene terephthalate (PET) is taken as an example, but the present invention is the same for other thermoplastic polyesters by measuring and quantifying predetermined end groups, decomposition amounts, etc. by ¹ H-NMR. Can be estimated. For example, ¹ H-NMR and NMR spectra such as PTT and PBT can be assigned with reference to Non-Patent Document 3.

  Step (b) is a step of degrading a part of the thermoplastic polyester sample. The deterioration process can be carried out by a test using ultraviolet rays that can be used for decomposing the thermoplastic polyester. For example, ultraviolet irradiation by an ultraviolet lamp, outdoor weather resistance test, accelerated weather resistance test and the like can be mentioned. In the present invention, the deterioration is preferably performed by an accelerated weathering test. In the present invention, the accelerated weathering test includes the following methods.

  The accelerated weather resistance test can be performed with a UVB (313) lamp based on JISK5600-7-8. In addition, the accelerated weather resistance test can be performed with a UVA (340) lamp based on JIS 5600-7-8. Further, the accelerated weathering test of JISK5600-7-7 using a xenon light source can be performed.

In step (c), ¹ H-NMR spectra of undegraded thermoplastic polyester and deteriorated thermoplastic polyester are measured, and the terminal amount of undegraded thermoplastic polyester and deteriorated thermoplastic polyester, decomposition of the ester structure of deteriorated thermoplastic polyester, This is a step of obtaining the number average molecular weight (Mn) by calculating the value (N; mol%) of the amount and the decomposition amount of the ether structure of the deteriorated thermoplastic polyester with respect to the total constitutional unit amount of the thermoplastic polyester.

  The value of N is calculated from each of the above amounts, and N can be obtained by the following (Equation 1).

  N = [(terminal amount of undegraded thermoplastic polyester) × 1/2] + (decomposition amount of ester structure of deteriorated thermoplastic polyester) + (decomposition amount of ether structure of deteriorated thermoplastic polyester) (Formula 1)

  The number average molecular weight (Mn) can be obtained from the value of N obtained in (Formula 1) by the following (Formula 2).

  Mn = [(Formula weight of composition formula of thermoplastic polyester) × 100] / N (Formula 2)

Here, the above (Formula 1) is converted in order to calculate the value of N from the functional group of the proton measurable by ¹ H-NMR. (Equation 1) can be converted as the following (Equation 3).

  N = [{(Amount of aromatic carboxylic acid terminal of undegraded thermoplastic polyester) + (Amount of alcohol terminal of undegraded thermoplastic polyester)} × 1/2] + (Aromatic carboxylic acid terminal of deteriorated thermoplastic polyester) Increase amount) + (decrease amount of ether structure of deteriorated thermoplastic polyester) (Formula 3)

  That is, (end amount of undegraded thermoplastic polyester) can be replaced by (amount of aromatic carboxylic acid end of undegraded thermoplastic polyester) + (amount of alcohol end of undegraded thermoplastic polyester), The amount of decomposition of the ester structure of the thermoplastic polyester and the amount of decomposition of the ether structure of the deteriorated thermoplastic polyester are respectively the increase amount of the aromatic carboxylic acid terminal of the deteriorated thermoplastic polyester and the ether structure of the deteriorated thermoplastic polyester. Can be replaced with a decrease amount).

  Further, (Expression 3) corresponds to the following (Expression 4).

  N = [{(Aromatic carboxylic acid terminal amount of undegraded thermoplastic polyester) + (Alcohol terminal amount of undegraded thermoplastic polyester)} × 1/2] + {(Aromatic carboxylic acid terminal amount of deteriorated thermoplastic polyester) )-(Aromatic carboxylic acid terminal amount of undegraded thermoplastic polyester)} + {(Ether structure amount of undegraded thermoplastic polyester)-(Ether structure amount of undegraded thermoplastic polyester)} (Formula 4)

  That is, (decomposition amount of ester structure of deteriorated thermoplastic polyester) can be calculated from {(end amount of aromatic carboxylic acid of deteriorated thermoplastic polyester) − (end amount of aromatic carboxylic acid of undegraded thermoplastic polyester)}. Further, (the amount of decrease in the ether structure of the deteriorated thermoplastic polyester) can be calculated from {(the amount of ether structure of the undegraded thermoplastic polyester) − (the amount of ether structure of the deteriorated thermoplastic polyester)}.

Therefore, if the aromatic carboxylic acid terminal amount of the undegraded and deteriorated thermoplastic polyester, the alcohol terminal amount of the undegraded thermoplastic polyester, and the ether structure amount of the undegraded and deteriorated thermoplastic polyester are obtained from ¹ H-NMR, The above N is obtained, and the number average molecular weight of the deteriorated thermoplastic polyester can be determined from (Equation 2). Each amount of the above (formula 3) and (formula 4) can be obtained by ¹ H-NMR measurement.

  In the present invention, a thermoplastic polyester is an object of measurement. In the process of production, the thermoplastic polyester is composed of alkylene glycols as raw materials for the thermoplastic polyester (for example, ethylene glycol for PET, trimethylene glycol for PTT, In PBT, 1,4-butanediol and the like are condensed to form a dihydric alcohol containing an ether structure. And the thermoplastic polyester by which the alcohol containing this ether structure was taken in into the polyester structure arises. For example, in PET, a polymer having the following structure in which diethylene glycol is incorporated is by-produced.

The present invention is characterized in that the amount thereof is quantified as described above from ¹ H-NMR of the ether structure of the thermoplastic polyester having this ether structure, and this is taken into account when calculating the N value. By taking into consideration the ether structure amount based on ¹ H-NMR of the ether structure of the thermoplastic polyester having this ether structure, there is a correlation between the number average molecular weight using the N value and the number average molecular weight measured by GPC. It has been revealed by the present inventors that it is more linear.

Next, the ¹ H-NMR study of the thermoplastic polyester is described in Non-Patent Document 3, and the assignment between the structure of the thermoplastic polyester and the peak of the ¹ H-NMR spectrum is reported.

The measurement of ¹ H-NMR was carried out using an undegraded and deteriorated thermoplastic polyester sample in a predetermined solvent (for example, 1,1,1,3,3,3-hexafluoro-2-isopropanol-d2 and chloroform-d in a volume ratio of 1). 1), and a small amount of a base such as isopropylamine is added. The reason for adding a base such as amine will be described below.

  A base such as an amine forms a salt with the terminal carboxyl group of the thermoplastic polyester. In the case of the present invention, the added isopropylamine reacts with an aromatic carboxylic acid end group to form a salt such as the following compound (B).

In the ¹ H-NMR spectrum of the thermoplastic polyester using the above-mentioned solvent, four protons on the aromatic ring are observed as a peak near δ 8.1 ppm. This is the same even in the case of a compound that does not form an amine salt, such as the compound (A) whose terminal is a carboxylic acid. That is, in the above compound (A), two protons on the aromatic ring on the carboxyl group side overlap in the ¹ H-NMR spectrum with a peak in the vicinity of δ8.1 ppm which is a signal of the proton on the aromatic ring. Yes. On the other hand, in an amine salt such as compound (B), two protons on the aromatic ring on the carboxyl group side can be identified as a peak near δ 7.9 ppm in the ¹ H-NMR spectrum. Thus, when measuring ¹ H-NMR, a desired peak can be separated and observed by adding a small amount of amine. In the present invention, the aromatic carboxylic acid terminal amount of the thermoplastic polyester is calculated from the integrated amount of the peak near δ7.9 ppm. Specifically, based on assignment of ¹ H-NMR peak when amine is added, the amount of aromatic carboxylic acid terminal is [(integral value of δ7.9 ppm peak) × 2] / [(δ7. 9 ppm peak integration value) + (δ 8.1 ppm peak integration value)].

Regarding the measured ¹ H-NMR of undegraded and deteriorated thermoplastic polyester, for example, in the case of PET, the peak of two protons on the aromatic ring on the side to which the carboxyl group is bonded at the end of the aromatic carboxylic acid of the thermoplastic polyester ( Equivalent to the terminal amount of aromatic carboxylic acid in thermoplastic polyester), peak of proton on carbon atom directly connected to oxygen atom at the alcohol terminal of thermoplastic polyester (corresponding to the terminal amount of alcohol in thermoplastic polyester), thermoplastic polyester The proton peak on the carbon atom (corresponding to the ether structure amount) directly connected to the oxygen atom of the ether structure is detected, and the mol% amount of each component is calculated from the integral value. The mol% amount of the alcohol terminal of the thermoplastic polyester is [(integral value of proton peak on carbon atom directly connected to oxygen atom of alcohol terminal of thermoplastic polyester (2H component near δ 4.0 ppm)) × 2 ] / [(Integral value of peak at δ7.9 ppm) + (integral value of peak at δ8.1 ppm)]]. The mol% amount of the ether structure of the thermoplastic polyester is [(integral value of proton peak on carbon atom directly connected to oxygen atom of ether structure of thermoplastic polyester (4H component near δ 3.95 ppm)] / [ (Integrated value of peak at δ7.9 ppm) + (Integrated value of peak at δ8.1 ppm)].

  Further, the total constituent unit amount of the thermoplastic polyester corresponds to a value obtained by calculating 1H with 4H as the sum of the integral amount of the peak at δ8.1 ppm and the integral amount of the peak at δ7.9 ppm.

From the comparison of these ¹ H-NMR peak areas, each term is calculated to determine the value of N. From the value of N, the number average molecular weight (Mn) of the undegraded thermoplastic polyester and the degraded thermoplastic polyester can be obtained using the above (Formula 2).

  The second of the present invention is a method for estimating the maximum stress of the thermoplastic polyester. The second invention will be described below.

  The method of the second present invention includes the following steps.

(A) preparing a sample of thermoplastic polyester;
(B) deteriorating the thermoplastic polyester to obtain a deteriorated thermoplastic polyester;
(C) The ¹ H-NMR spectrum of undegraded thermoplastic polyester (undegraded thermoplastic polyester) and degraded thermoplastic polyester is measured, and the terminal amounts of undegraded thermoplastic polyester and degraded thermoplastic polyester, degraded thermoplastic polyester A step of calculating the decomposition amount of the ester structure and the decomposition amount of the ether structure of the deteriorated thermoplastic polyester as a mol% (N) with respect to all the structural units of the thermoplastic polyester, from the following formula (Formula 1):
N = [(terminal amount of undegraded thermoplastic polyester) × 1/2] + (decomposition amount of ester structure of deteriorated thermoplastic polyester) + (decomposition amount of ether structure of deteriorated thermoplastic polyester) (Formula 1)
(D) measuring the tensile strength of the undegraded thermoplastic polyester and the degraded thermoplastic polyester, and obtaining a correlation between the value of N and the tensile strength;
(E) Prepare an unknown sample of the thermoplastic polyester whose maximum stress is to be measured, calculate N of the unknown sample according to steps (b) and (c), and calculate the maximum stress of the unknown sample from the correlation of step (d) The process of estimating.

The procedure for calculating the N value in step (a), step (b) and step (c) of the second invention is the same as in the first invention. For example, the above-described value of N (mol%) is calculated from the ¹ H-NMR spectrum of the thermoplastic polyester that has not been deteriorated by the accelerated weather resistance test and the deteriorated thermoplastic polyester.

The step (d) is obtained from the value of N and the tensile strength calculated in the step (c) by measuring the tensile strength of the same undegraded thermoplastic polyester as measured by ¹ H-NMR and the degraded thermoplastic polyester. This is a step of obtaining a correlation between the maximum stresses (MPa).

  The tensile strength can be carried out with a predetermined tensile strength with respect to an appropriate test piece according to JISK7127. For example, the test piece type 5 can be used as the test piece, and the measurement can be performed at a tensile speed of 5 mm / min.

  The correlation between the maximum stress value obtained from the tensile strength test and the calculated N value is obtained. The correlation can be associated as a graph as shown in FIG.

  In step (e), an unknown sample of the thermoplastic polyester whose maximum stress is to be measured is prepared, N of the unknown sample is calculated according to steps (b) and (c), and the unknown sample is calculated from the correlation in step (d). This is a step of estimating the maximum stress.

  What is necessary is just to measure the value of N of an unknown sample similarly to the said process (b) and process (c). Next, as shown in FIG. 2, the maximum stress of the unknown sample can be estimated from the N value of the unknown sample using the previously created correlation graph.

  The present invention will be described in more detail with reference to the following examples. However, the following examples are not intended to limit the present invention.

Example 1
This example relates to a method for estimating the number average molecular weight, and this estimation method will be described in detail.

  27 PET films (15 cm × 7.5 cm × 0.5 mm) were prepared. Three sheets are samples of undegraded thermoplastic polyester (also referred to as undegraded samples in this example), and the remaining 24 sheets are subjected to an accelerated weather resistance test for 200 hours to 1600 hours (three sheets every 200 hours of test time). And a deteriorated thermoplastic polyester sample (also referred to as a deteriorated sample in this example).

  The accelerated weather resistance test was performed with a UVB (313) lamp according to JISK5600-7-8.

About 2 samples of the undegraded sample and the degraded sample, 5 mg of the surface layer is scraped out to about 0.05 mm (3 to 10 mg is preferably used as the measurement sample), and ¹ H-NMR measurement is performed (undegraded thermoplastic polyester The terminal amount of, the amount of degradation of the ester structure of the deteriorated thermoplastic polyester, and the amount of decomposition of the ether structure of the deteriorated thermoplastic polyester were determined.

First, the measurement conditions of ¹ H-NMR, the detection position of the peak of the molecular structure of interest, and the quantitative method will be described.

The sample obtained as described above was dissolved in 1,1,1,3,3,3-hexafluoro-2-isopropanol-d2 and chloroform-d mixed at a volume ratio of 1: 1, and isopropyl was dissolved. additives such as amine 1 drops of result of ¹ H-NMR measurement at 50 ° C. (refer to non-Patent Document 3). Bases such as isopropylamine form salts with terminal carboxyl groups. When the additive is isopropylamine, this reacts with the aromatic carboxylic acid end group to form a salt such as compound (B) below.

In the ¹ H-NMR spectrum of the thermoplastic polyester using the above-mentioned solvent, there are four protons on the aromatic ring forming an ester bond and an aromatic having a terminal carboxyl group such as compound (A). Four protons on the ring are observed as non-separated peaks as peaks near δ 8.1 ppm. That is, in the ¹ H-NMR spectrum, the proton signal on the aromatic ring, which is a constituent element of the thermoplastic polyester, overlaps with a peak near δ 8.1 ppm. On the other hand, in an amine salt such as compound (B), two protons on the aromatic ring on the carboxyl group side can be identified as a doublet-like peak near δ7.9 ppm in the ¹ H-NMR spectrum. . As described above, the doublet-like peak detected in the vicinity of δ 7.9 ppm is formed on the aromatic ring on the side where the carboxylate is bonded, with the aromatic carboxylic acid terminal of the thermoplastic polyester forming a salt with isopropylamine. Two proton peaks (2H min). In addition, the triplet-like peak detected near δ 4.0 ppm is a proton peak (2H portion) directly connected to the oxygen atom at the alcohol end of the thermoplastic polyester, and around δ 3.95 ppm. The triplet-like peak detected is a proton peak (for 4H) on the carbon atom directly connected to the oxygen atom of the ether structure of the thermoplastic polyester. Therefore, mol% of the alcohol terminal amount of the thermoplastic polyester is [(the integrated value of the proton peak on the carbon atom directly connected to the oxygen atom at the alcohol terminal of the thermoplastic polyester (2H component near δ 4.0 ppm)). × 2] / [(integral value of δ7.9 ppm peak) + (integral value of δ8.1 ppm peak)]]. In addition, mol% of the ether structure amount of the thermoplastic polyester is [(integral value of a proton peak on a carbon atom directly connected to an oxygen atom of the ether structure of the thermoplastic polyester (4H component near δ 3.95 ppm)] / [ (Integrated value of δ 7.9 ppm peak) + (Integrated value of δ 8.1 ppm peak)] The attribution of each ¹ H-NMR peak of the thermoplastic polyester refers to Non-Patent Document 3. be able to.

3 and 4 show charts of the ¹ H-NMR spectrum of the PET described above. FIG. 3 is a peak of the characteristic portion, and FIG. 4 is an enlarged view of the spectrum of FIG. 3 from around δ3.7 to around δ5.0.

  The content of each molecular structure was calculated as a mol% with respect to all structural units using the peak integral value. As the amount of all structural units, the sum of the integral value of the peak near δ7.9 ppm and the integral value of the peak near δ8.1 ppm was used.

Based on the genus of the peak of ¹ H-NMR when the above amine is added, the amount of aromatic carboxylic acid end is [(integral value of δ7.9 ppm peak) × 2] / [(δ 7.9 ppm peak). Integral value) + (integral value of the peak at δ 8.1 ppm)].

  The alcohol terminal amount of the undegraded thermoplastic polyester sample was 1.4 mol%, and the measurement results of the aromatic carboxylic acid terminal amount and the ether structure amount of the undegraded and deteriorated thermoplastic polyester sample were as shown in Table 1. .

  From the measurement result of the undegraded sample, the terminal amount of the undegraded thermoplastic polyester sample was determined as follows.

(Terminal amount of undegraded thermoplastic polyester sample [mol%])
= (Aromatic carboxylic acid terminal amount of undegraded thermoplastic polyester sample [mol%]) + (Alcohol structure amount of undegraded thermoplastic polyester sample [mol%])
= 0.4 [mol%] + 1.4 [mol%] = 1.8 [mol%]

  Moreover, (the amount of aromatic carboxylic acid terminal increase of the deteriorated thermoplastic polyester sample) = (the amount of aromatic carboxylic acid terminal of the deteriorated thermoplastic polyester sample) − (the amount of aromatic carboxylic acid terminal of the undegraded thermoplastic polyester sample) , (Ether structure decrease amount of deteriorated thermoplastic polyester sample) = (ether structure amount of undegraded thermoplastic polyester sample) − (ether structure amount of deteriorated thermoplastic polyester sample). Therefore, when these were calculated, the values in Table 2 were obtained.

  Using the terminal amount of the above-mentioned undegraded thermoplastic polyester sample and the values shown in Table 2, the following N value was calculated.

N = [(Terminal amount of undegraded thermoplastic polyester sample) × 1/2] + (Increased amount of aromatic carboxylic acid terminal of deteriorated thermoplastic polyester sample) + (Decrease in ether structure of deteriorated thermoplastic polyester sample)

  The number average molecular weight (Mn) was estimated and calculated from the obtained N value by the following formula.

Mn = (formula weight of composition formula) × 100 / N = 192 × 100 / N
(PET formula weight: 192)

  The results are shown in Table 3.

  In addition, when the number average molecular weight of these samples was measured by GPC, it was as shown in Table 4.

FIG. 5 shows the correlation between Mn measured using GPC and Mn obtained using the N value calculated from the result of ¹ H-NMR measurement. When the correlation obtained in FIG. 5 was approximated by a straight line passing through the origin, the slope was 0.967, and the R-square value was 0.983. From the above results, it was confirmed that the number average molecular weight (Mn) obtained using N calculated for NMR measurement was almost the same as the number average molecular weight (Mn) measured using GPC.

  In the present invention, a thermoplastic polyester is an object of measurement, but some thermoplastic polyesters contain an ether structure in their molecular structure. For example, polyethylene terephthalate (PET), which is a representative example of thermoplastic polyester, is synthesized by dehydration condensation of terephthalic acid and ethylene glycol or transesterification of dimethyl terephthalate and ethylene glycol. In this reaction process, Glycols are dehydrated and condensed to produce diethylene glycol, which reacts with terephthalic acid or terephthalic acid ester, and by-product having an ether structure in the PET molecular chain represented by the following chemical formula.

The present invention is characterized in that the amount is quantitatively determined from ¹ H-NMR of the ether structure of the thermoplastic polyester having the ether structure, and this amount is taken into consideration when calculating the N value.

  In the following, the advantages of taking into account a thermoplastic polyester having such an ether structure will be described.

  Such an ether structure is found not only in PET but also in thermoplastic polyester, but its content is generally as low as 10 mol% or less. For this reason, conventionally, in the analysis of the deteriorated sample of the thermoplastic polyester, only the aromatic carboxylic acid terminal has been focused, and the decomposition of the ether structure due to the deterioration has been overlooked (Non-patent Document 4). However, since the ether structure is more easily decomposed by light than the ester structure, it is necessary to evaluate not only the decomposition of the ester structure but also the decomposition of the ether structure in order to accurately evaluate the amount of molecular chain cleavage due to deterioration. .

  Below, the result in the case where the decomposition of the ether structure is not taken into consideration is shown for the same sample as the sample described above in this example.

  Specifically, N ′ in the following (formula 5) is used in place of N.

N ′ = [(end amount of undegraded thermoplastic polyester sample) × 1/2] + (increase amount of aromatic carboxylic acid end of deteriorated thermoplastic polyester sample) (Formula 5)

  When N ′ is calculated from Table 2 and Mn is calculated, Table 5 is obtained.

FIG. 6 shows the correlation between Mn measured using GPC and Mn obtained using the N ′ value calculated from the result of ¹ H-NMR measurement. When the correlation obtained in FIG. 6 was approximated by a straight line passing through the origin, the slope was 1.126, and the R-square value was 0.804. From the above results, the number-average molecular weight (Mn) determined using N ′ calculated for NMR measurement was greatly reduced in accuracy of approximation as compared with the case where Mn was calculated using the above N value. Thereby, it turns out that it is necessary to consider the decomposition | disassembly of the ether structure of thermoplastic polyester.

(Example 2)
In this embodiment, a method for estimating the maximum stress will be described. First, the sample used in Example 1 was subjected to a tensile test, the maximum stress was measured, and the correlation between N and the maximum stress was graphed.

  The tensile test was measured according to JISK7127 using a specimen type 5 at a tensile speed of 5 mm / min.

  Tensile tests were carried out 5 times (n = 5) for each test piece, and the average value of the maximum stress was determined. The results are shown in Table 6. N is a reprint of the value obtained in Example 1.

  The relationship between the N value and the maximum stress is shown in FIG.

Next, ¹ H-NMR was measured in the same manner as in Example 1 for an undegraded thermoplastic polyester sample and a degraded thermoplastic polyester sample of a PET film (also referred to as an unknown sample in this example) for which maximum stress was to be estimated. .

  The alcohol end amount of the undegraded thermoplastic polyester sample was 0.4 mol%. Moreover, the aromatic carboxylic acid terminal amount and ether structure amount of the thermoplastic polyester of the undegraded sample and the deteriorated sample were the values shown in Table 7.

(Terminal amount [mol%] of undegraded thermoplastic polyester sample) = (Aromatic carboxylic acid terminal amount [mol%] of undegraded thermoplastic polyester sample) + (Alcohol structure amount [mol%] of undegraded thermoplastic polyester sample ])
= 1.2 [mol%] + 0.4 [mol%] = 1.6 [mol%]

  From the above results, when the increase amount of the aromatic carboxylic acid terminal and the decomposition amount of the ether structure were determined and N was calculated, the values shown in Table 8 were obtained.

  When the maximum stress corresponding to the calculated N = 8.8 was read from the graph of FIG. 7, it was about 47 MPa. This is an estimate of the maximum stress.

When the above-mentioned unknown sample was actually subjected to a tensile test and the maximum stress was measured, it was 45 MPa. It can be seen that this value is relatively close to the estimated value (about 47 MPa) obtained from the N value obtained by ¹ H-NMR measurement.

  The method for estimating the maximum stress of the present invention is also characterized in that the ether structure amount of the thermoplastic polyester is measured. The superiority of this point is shown below.

In the following, for the same sample as the sample for which the maximum stress measurement and ¹ H-NMR measurement were performed in this example, the decomposition of the ether structure of the thermoplastic polyester was not taken into account, but instead of N, the following N ′ The value was calculated.

    N ′ = [(end amount of undegraded thermoplastic polyester sample) × 1/2] + (increase amount of aromatic carboxylic acid end of deteriorated thermoplastic polyester sample)

  First, Table 9 summarizes the correspondence between the N ′ value obtained in Example 1 and the maximum stress measured in Example 2. A graph showing the relationship between the N 'value and the maximum stress is shown in FIG.

Next, N ′ of the unknown sample was determined from the ¹ H-NMR measurement result of the unknown sample as described below.

    N '= 0.8 + 2.9 = 3.7

  When the maximum stress corresponding to this is obtained from FIG. 8, it is about 58 Mpa. That is, this result was presumed that the deterioration was not sufficiently advanced yet and the decrease in the maximum stress did not begin. However, the actual tensile test result was about 45 MPa, and the maximum stress was reduced.

  This result indicates that the photodecomposition of the ether structure of the thermoplastic polyester also contributes to the maximum stress reduction. Therefore, in order to estimate the maximum stress based on the molecular chain breakage of the thermoplastic polyester due to deterioration, not only the amount of carboxylic acid terminal of the thermoplastic polyester is quantified as a degradation product due to deterioration, but also thermoplasticity. It shows that it is important to measure the degradation amount of the ether structure of polyester.

Claims (6)

A method for estimating the number average molecular weight of a thermoplastic polyester,
(A) preparing a sample of thermoplastic polyester;
(B) deteriorating the thermoplastic polyester to obtain a deteriorated thermoplastic polyester;
(C) The ¹ H-NMR spectrum of undegraded thermoplastic polyester (undegraded thermoplastic polyester) and degraded thermoplastic polyester is measured, and the terminal amounts of undegraded thermoplastic polyester and degraded thermoplastic polyester, degraded thermoplastic polyester The amount of decomposition of the ester structure and the amount of decomposition of the ether structure of the deteriorated thermoplastic polyester are calculated from the following formula (Formula 1) as mol% (N) with respect to all the structural units of the thermoplastic polyester,
N = [(terminal amount of undegraded thermoplastic polyester) × 1/2] + (decomposition amount of ester structure of deteriorated thermoplastic polyester) + (decomposition amount of ether structure of deteriorated thermoplastic polyester) (Formula 1)
Step of obtaining number average molecular weight (Mn) from the following formula (Formula 2): Mn = [(Formula weight of composition formula of thermoplastic polyester) × 100] / N (Formula 2)
A method for estimating the number average molecular weight of a thermoplastic polyester.   The method of estimating a number average molecular weight of a thermoplastic polyester according to claim 1, wherein the thermoplastic polyester is deteriorated by an accelerated weather resistance test in the step (b). The degradation amount of the ester structure of the deteriorated thermoplastic polyester is defined as the increase amount of the aromatic carboxylic acid terminal in the ¹ H-NMR spectrum of the deteriorated thermoplastic polyester, and the decomposition amount of the ether structure of the deteriorated thermoplastic polyester is defined as the deteriorated thermoplastic polyester. The method for estimating the number average molecular weight of a thermoplastic polyester according to claim 1 or 2 quantified as a reduction amount of an ether structure in a ¹ H-NMR spectrum of the polyester. A method for estimating the maximum stress of a thermoplastic polyester,
(A) preparing a sample of thermoplastic polyester;
(B) deteriorating the thermoplastic polyester to obtain a deteriorated thermoplastic polyester;
(C) The ¹ H-NMR spectrum of undegraded thermoplastic polyester (undegraded thermoplastic polyester) and degraded thermoplastic polyester is measured, and the terminal amounts of undegraded thermoplastic polyester and degraded thermoplastic polyester, degraded thermoplastic polyester A step of calculating the decomposition amount of the ester structure and the decomposition amount of the ether structure of the deteriorated thermoplastic polyester as a mol% (N) with respect to all the structural units of the thermoplastic polyester, from the following formula (Formula 1):
N = [(terminal amount in undegraded sample) × 1/2] + (ester structure decomposition amount) + (ether structure decomposition amount) (Formula 1)
(D) measuring the tensile strength of the undegraded thermoplastic polyester and the degraded thermoplastic polyester, and obtaining a correlation between the value of N and the tensile strength;
(E) Prepare an unknown sample of the thermoplastic polyester whose maximum stress is to be measured, calculate N of the unknown sample according to steps (b) and (c), and calculate the maximum stress of the unknown sample from the correlation of step (d) A method for estimating the maximum stress, including the step of estimating   The method for estimating the maximum stress of the thermoplastic polyester according to claim 4, wherein in the step (b), the thermoplastic polyester is deteriorated by an accelerated weather resistance test. The degradation amount of the ester structure of the deteriorated thermoplastic polyester is defined as the increase amount of the aromatic carboxylic acid terminal in the ¹ H-NMR spectrum of the deteriorated thermoplastic polyester, and the decomposition amount of the ether structure of the deteriorated thermoplastic polyester is defined as the deteriorated thermoplastic polyester. The method for estimating the maximum stress according to claim 4, wherein the method is quantified as a reduction amount of an ether structure in a ¹ H-NMR spectrum of the polyester.

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