JPH10168168A - Method for producing polyester copolymer - Google Patents

Abstract

(57) [Problem] To provide a polyester for a bottle which is excellent in transparency and generates little acetaldehyde, formaldehyde and oligomer. A method for producing a polyester copolymer, wherein terephthalic acid is used as an acid component, ethylene glycol and diethylene glycol are used as glycol components, and the copolymerization ratio of diethylene glycol is 2.0 to 4.0% by weight of the polyester copolymer. A method for producing a polyester copolymer for bottles, wherein substantially non-crystalline germanium dioxide is used as a polymerization catalyst, and the timing of adding the polymerization catalyst is at a point when the esterification rate reaches 90% or more. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester copolymer for bottles, and more particularly to a polyester copolymer excellent in transparency and productivity, which causes whitening of a molded article, an amount of oligomer in a molded article which causes an unpleasant odor, and formaldehyde. The present invention relates to a method for producing a polyester copolymer for a bottle having a low content of impurities such as acetic acid and acetaldehyde.

[0002]

2. Description of the Related Art Polyester is widely used for fibers, films, bottles, industrial resins and the like because of its excellent mechanical, physical and chemical properties.

[0003] In particular, when a bottle is processed as a molded product, the transparency of the bottle is important for external reasons.
There is a need for polyesters that can provide bottles with good transparency.

[0004] One of the factors impairing the transparency is the so-called internal haze caused by the catalyst used in producing the polyester, and the crystallization and opacity of the polyester itself induced by catalyst particles.

Various catalysts have been used in the production of polyesters. One of the most widely used is an antimony catalyst, which remains as particles in the polymer due to its low solubility in polyester and significantly reduces the transparency of the molded article.

On the other hand, the titanium catalyst has a relatively high transparency since it has a high solubility in a polymer and can suppress the haze low and does not particularly promote the crystallization. However, this catalyst promotes the degradation of the polyester at high temperatures. There is a problem that the polyester itself turns yellow.

[0007] In this respect, the germanium catalyst has high solubility in the polymer, has relatively good transparency, and the coloring of the polyester itself is not a disadvantage compared to the titanium catalyst.

[0008]

However, even when a germanium catalyst is used, transparency cannot be said to be sufficient yet in fields where the required quality is severe, such as bottles for mineral water, and transparency is still better in such fields. Polyester that gives a perfect bottle is required.

In addition, polyester polymers for bottles include:
There is a strong demand for reducing the cost as much as possible and for minimizing the amount of oligomers, acetaldehyde and formaldehyde, which may cause the yield of molded articles and cause offensive odor, in the final molded articles as much as possible.

It is an object of the present invention to provide a polyester for a bottle which can be particularly suitably used as a bottle, has excellent transparency, and generates little acetaldehyde, formaldehyde and oligomer.

[0011]

According to the present invention, terephthalic acid is used as an acid component, ethylene glycol and diethylene glycol are used as glycol components, and the copolymerization ratio of diethylene glycol is 2.0 to 4.0% by weight of the polyester copolymer. A method for producing a polyester copolymer for a bottle, wherein substantially non-crystalline germanium dioxide is used as a polymerization catalyst, and the timing of addition of the polymerization catalyst is 90%.
% Of the polyester copolymer for a bottle, characterized in that it is at the point of time when the amount reaches at least%.

The polyester copolymer of the present invention is a polyester copolymer produced from terephthalic acid and ethylene glycol and diethylene glycol by a direct polymerization method.

The copolymerization ratio of diethylene glycol is 2.0 to 4.0% by weight based on the total amount of the polyester copolymer.

When the copolymerization ratio of diethylene glycol is 2.
When the amount is less than 0% by weight, the effect of improving the productivity due to the increase in the solid-state polymerization rate is small, the diffusion effect of impurities such as formaldehyde and acetaldehyde in the solid-state polymerization step is small, and the transparency is low. The level of polyethylene terephthalate present in the water does not differ.

The diethylene glycol copolymerization ratio is 4.0
When the content is more than 10% by weight, not only is it very difficult to control the crystallization conditions for avoiding the fusion of chips during the solid-state polymerization, but also the heat resistance and the bottle strength deteriorate.
The coloring is conspicuous, and on the contrary, the off-flavor due to acetaldehyde, formaldehyde and the like becomes stronger.

When the copolymerization ratio of diethylene glycol is 2.0 to 4.0% by weight based on the total amount of the copolymer, the whitening phenomenon of the bottle can be suppressed. Further, the crystallization speed during the solid-phase polymerization is slowed, and low molecular weight impurities such as oligomers, acetaldehyde, and formaldehyde can be easily scattered from the polymer in the production process, so that the amount of the remaining oligomer when the bottle is formed can be suppressed. Further, the scattering rate of ethylene glycol from the polymer, which is the rate-determining step of the solid-state polymerization reaction, is improved, and the solid-state polymerization rate can be increased, so that productivity can be improved.
Furthermore, the molding temperature can be lowered, the degradation reaction when molding the polymer after solid phase polymerization can be suppressed, and finally the amount of oligomer, acetaldehyde and formaldehyde contained in the molded product should be reduced. Is possible.

In the present invention, the polyester copolymer may be copolymerized with terephthalic acid and a third component other than ethylene glycol and diethylene glycol. The proportion of the third component is required to be within a range that does not impair the object of the present invention, and is 5 mol% or less, preferably 2 mol% or less of all the acid components. In order to improve transparency, productivity, and moldability, the amount of the third component is preferably as small as possible, and it is particularly preferable that the third component is not copolymerized.

As the third component, aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylether dicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; fatty acid dicarboxylic acids such as adipic acid and sebacic acid; diethylene glycol; Aliphatic diols such as triethylene glycol, tetramethylene glycol, hexamethylene glycol; alicyclic diols such as cyclohexanediol and cyclohexane dimethanol; aromatic diols such as naphthalene diol, bisphenol A and resorcin;
Examples thereof include oxycarboxylic acids such as oxybenzoic acid, m-oxybenzoic acid, salicylic acid, mandelic acid, hydroacrylic acid, glycolic acid, 3-oxypropionic acid, asiatic acid, and quinovanic acid.

The trifunctional or higher polyfunctional compound such as glycerin, trimethylolpropane, pentaerythritol, or the like, in a range where the polyester is substantially linear.
Trimellitic acid, trimesic acid, pyromellitic acid, tricarballylic acid, gallic acid and the like may be copolymerized, and if necessary, a monofunctional compound such as o-benzoylbenzoic acid,
Naphthoic acid may be used as the third component.

In the present invention, substantially amorphous germanium dioxide is used as a polycondensation catalyst. The substantially amorphous germanium dioxide does not contain or contains crystal grains, the crystal grain size is 25 nm or less, no peak is observed by Raman spectrum, and the specific gravity is 3.8 g / cm. Germanium dioxide which is ³ or less. If the polycondensation catalyst is not substantially amorphous germanium dioxide, the transparency will be poor and the quality for bottles cannot be maintained.

If importance is placed on the effect of transparency, it is preferable to use substantially amorphous germanium for the entire amount of the polycondensation catalyst. The reason for the increased transparency is not clear,
The fact that substantially amorphous germanium dioxide has high solubility in ethylene glycol and a polymer is presumed to be the reason that the transparency is improved as compared with a polymer using crystalline germanium dioxide.

The amorphous germanium dioxide must be added at a time when the esterification rate reaches 90% or more. Before this point, a large amount of water is by-produced during the esterification reaction, and the added germanium dioxide easily transitions to a stable form having a high specific gravity, and the germanium dioxide particles are agglomerated. Even if molded polyester is used, a bottle having sufficient transparency cannot be obtained.

As a method of adding germanium dioxide,
It is preferably added as a 0.5 to 3% by weight ethylene glycol solution. At this time, a small amount of a basic compound may be present to enhance the solution stability.

In the present invention, germanium dioxide which distills out of the system together with ethylene glycol at the stage when the esterification reaction has progressed by 90% or more, preferably 93% or more in terms of the esterification rate, is returned to the system and polymerized. It is preferably used as a catalyst. The amorphous germanium dioxide distilled out together with the ethylene glycol changes to a stable form having a high specific gravity in the presence of water and cannot be reused as the amorphous germanium dioxide. Most of the emitted or scattered germanium dioxide remains substantially amorphous,
It can be returned to the system and reused. It is preferable to return the system to the system after the esterification ratio reaches 90% or more, preferably 93% or more.

The polyester polymer for a bottle of the present invention can be obtained, for example, by directly esterifying an acid and a diol, adding a substantially amorphous germanium dioxide, and then performing a melt polycondensation. At this time, it is preferable to adjust the amount of diethylene glycol to be added so that the amount of diethylene glycol as a copolymer component is 2.0 to 4.0% by weight based on the total amount of the copolymer. Since the specific addition amount varies depending on the reaction apparatus, it is preferable to appropriately adjust the addition amount. If necessary, other additives such as a tinting agent, a coloring agent, an antioxidant, an ultraviolet absorber, an antistatic agent or a flame retardant may be used. After completion of the melt polycondensation, for example, the mixture is melt-extruded, cooled in a suitable cooling medium, for example, water, and cut into a suitable size to form chips. The tip may be a rectangular parallelepiped, a cylinder, a die, or a sphere.

This polyester copolymer is subjected to solid-phase polymerization and used for bottle molding. The bottle can be formed by a known method.

[0027]

The present invention will be described in detail with reference to the following examples. In addition,
In the examples, "parts" means parts by weight. The method for measuring the characteristics used in the examples is shown below.

1) Intrinsic viscosity number [η]: Calculated from the solution viscosity measured at 35 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 60/40).

2) Transparency of molded article: 160
After drying at 5 ° C. for 5 hours, using an injection molding machine Dynamelter M-100DM manufactured by Meiki Seisakusho, cylinder temperature 28
A preform of 50 g was molded at 0 to 290 ° C. (Tm + 40 ° C.) and blow-stretched to obtain a bottle having an inner volume of 1.5 liter and a body thickness of 0.3 mm. The straight body was cut off, and the haze of the bottle body was measured with a haze meter to determine the haze of the bottle. A color and color difference metal model 1001DP manufactured by Nippon Denshoku Industries Co., Ltd. was used as the haze meter.

3) Specific gravity: Measured at 25 ° C. using an ultra pycnometer (manufactured by Yuasa Ionics), and the average of 15 measurements was taken as the value of the specific gravity.

4) Copolymerization ratio of diethylene glycol (DEG) 200 g of the polymer and 10 ml of hydrazine hydrate (hydrazine monohydrate) were mixed, and the polymer was completely decomposed at 150 ° C. for 10 minutes. The solution was analyzed by gas chromatography, and the proportion of diethylene glycol copolymerized in the polymer was determined from the detected concentration. For gas chromatography, gas chroma 263 manufactured by Hitachi, Ltd. was used.

5) Amount of Cyclic Trimer Oligomer (Cy-3) Generated 5 mg of a sample of the polymer after solid-phase polymerization or a straight body portion of the bottle molded product obtained in 2) was precisely weighed to obtain hexafluoroisopropanol (HFIP). / CHCl ₃ = 0.2 ml /
It was dissolved in 0.2 ml, diluted with CHCl ₃ to an appropriate concentration, and the amount of the cyclic trimer oligomer was measured by gel permeation chromatography. For gel permeation chromatography (GPC), GPC manufactured by Water was used, and a column for measuring cyclic trimer oligomer (TSK-GFL2000H8 * 2 manufactured by Tosoh) was used as a column.

6) Amount of formaldehyde (FA) and acetaldehyde (AA) The solid body of the solid-state polymerized polymer or the bottle obtained in 2) is cooled with liquid nitrogen and then pulverized to obtain a polymer sample having a size of 20 mesh or less. 1.0 g was collected.

[0034] 3.0 ml of water was added to the sample, and 12
Acetaldehyde and formaldehyde were extracted by heating at 0 ° C. for 1 hour. 2,4-DNPH (2,
4-dinitrophenylhydrazine) to formaldehyde and acetaldehyde as their stable organic salts.
Further extraction into Cl ₄ . The CCl ₄ was analyzed by gas chromatography, and the amounts of formaldehyde and acetaldehyde contained in the polymer in the bottle were calculated from the amounts of detected salts. For gas chromatography, gas chroma 263 manufactured by Hitachi, Ltd. was used.

7) DSC (Differential Scanning Calorimeter) Analysis Thermal Analysis 2200 manufactured by TA Instruments
Measurements were made using a type differential scanning calorimeter. Put 10.0mg of polymer chip sample in aluminum pan and add 20mg
After heating to 300 ° C at a heating rate of ° C / min,
Quenched quickly and without direct water contact in a test tube immersed in an ice bath. Then again at 20 ° C / mi
n, the crystallization temperature Tc and the melting point Tm were determined.
When the temperature reaches 10 ° C, the temperature is maintained for 2 minutes.
/ Min. At that time, the crystallization peak at the time of temperature drop is T
cd. Tci, Tm, and Tcd each read the maximum point of the peak.

8) Crystal particle size Using X-ray diffraction measurement data, the crystal particle size at 2θ = 38 ° and 60 ° was calculated by Scherrer equation (α (Å) =
Kλ / Bcos θ α: crystal particle size K constant = 0.
9 λ: 1.54Å β: half width of the measured peak), and the average value was used as the crystal grain size. An X-ray diffractometer manufactured by Rigaku Denki Kogyo KK was used for the X-ray diffractometer.

9) Raman spectrum The Raman spectrum was analyzed by laser Raman spectroscopy. The measurement conditions are as follows. Measurement conditions ・ Excitation light source Argon ion laser (wavelength: 488n
m) Sample preparation A sample was filled in a glass NMR tube under a nitrogen atmosphere and measured.・ Detector Photomultiplier tube (PM) ・ Measurement conditions slit 200μm laser 150mW The measuring device is Jobin-Yvon
n) A Ramanor U-1000 Raman system manufactured by the company was used.

Example 1 3600 parts of terephthalic acid and 2100 parts of ethylene glycol were slurried at room temperature.
The mixture was charged into an autoclave equipped with a stirrer and reacted at 270 ° C. under a pressure of 3 kg / cm ² . When the amount of distilled water reached 600 parts, the pressure was released, and the reaction was further performed at 270 ° C. under normal pressure. Further, when the amount of distilled water becomes 740 parts or more, germanium dioxide shown in Table 1 is added as germanium, and 30 mmol% (relative to terephthalic acid) and trimethyl phosphate are added to 3.0 parts, and diethylene glycol is added to the amount shown in Table 1. And then 0.1 mmH at 285 ° C
The polycondensation reaction was carried out under a reduced pressure of about 2.5 hours to obtain a polyester copolymer having an intrinsic viscosity of 0.62.

This polyester copolymer was used for 0.5 mm
Solid-state polymerization was performed at 210 ° C. under an N ₂ atmosphere of Hg to increase the intrinsic viscosity of the polymer to 0.75.

Table 2 shows the quality of the polymer after the solid phase polymerization and the quality of the bottle molded using this polymer.

[0041]

[Table 1]

[0042]

[Table 2]

Example 2, Comparative Examples 1 and 2 Example 1 was repeated except that diethylene glycol was added so that the amount of diethylene glycol in the prepolymer was as shown in Table 1.
A polyester copolymer was obtained in the same manner as described above. Table 2 shows the polymer quality and the bottle quality after the solid phase polymerization.

Example 3 A polyester copolymer was obtained in the same manner as in Example 1, except that amorphous germanium dioxide was added as an ethylene glycol slurry. Table 2 shows polymer quality and bottle quality after solid-state polymerization
It was shown to.

Comparative Example 3 A polyester copolymer was obtained in the same manner as in Example 1 except that hexagonal germanium dioxide was added in the form of an ethylene glycol slurry instead of amorphous germanium dioxide. Table 2 shows the polymer quality and the bottle quality after the solid phase polymerization.

Comparative Example 4 Example 1 was repeated except that the amorphous germanium dioxide was added at the beginning of the esterification reaction.
A polyester copolymer was obtained in the same manner as described above. Table 2 shows the quality of the solid-phase polymerized polymer and the quality of the bottle.

As can be seen from these results, a polymer having a diethylene glycol copolymerization ratio of less than 2.0% by weight has a low solid-state polymerization rate, a high Tcd and a high melting point, so that the molding temperature must be set to a high temperature. However, the increase in formaldehyde, acetaldehyde, and cyclic trimer oligomer (Cy-3) during molding is high (Comparative Example 1).
On the other hand, the diethylene glycol copolymerization ratio was 4.0.
If the amount is more than 10% by weight, the heat resistance rapidly deteriorates, and the yellow coloring of the polymer after solid-phase polymerization and the increase in formaldehyde and acetaldehyde during molding are unpreferably large (Comparative Example 2). If a hexagonal germanium dioxide is used instead of an amorphous one, the haze of the bottle becomes different. Amorphous is more and more preferable (Comparative Example 3).
On the other hand, if the entire amount of amorphous germanium dioxide is added at a time when the esterification rate is low, the water generated in the reaction system may change germanium dioxide to hexagonal, or there is an advantage to using amorphous germanium dioxide any longer. No (Comparative Example 4).

[0048]

EFFECT OF THE INVENTION The polyester copolymer of the present invention is a high-quality polyester copolymer having excellent transparency and capable of suppressing the amounts of oligomers, formaldehyde and acetaldehyde in solid-state polymers and molded articles to a low level. It is.

The polyester copolymer of the present invention can be particularly suitably used for packaging applications such as food packaging films and bottles.

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[Procedure amendment]

[Submission date] October 7, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

In addition, polyester polymers for bottles include:
To minimize costs, and to lower the yield of molded products, oligomers that may cause odor,
Acetaldehyde, there is a strong request had One in suppressing as much as possible reduce the formaldehyde in the final molded article.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

In the present invention, the polyester copolymer may be copolymerized with terephthalic acid and a third component other than ethylene glycol and diethylene glycol. The proportion of the third component is required to be within a range that does not impair the object of the present invention, and is 5 mol% or less, preferably 2 mol% or less of all the acid components. Excess third component in the specified amount of DEG
Crystallized polyesters have too poor crystallinity,
Unsatisfactory bottle strength or copolymerization
There is a concern that the flavor of the filling may deteriorate depending on the ingredients.
is there. Therefore, especially the third component other than DEG is copolymerized.
No PET is preferred.

Claims (1)

[Claims] 1. A polyester copolymer for bottles wherein terephthalic acid is an acid component, ethylene glycol and diethylene glycol are glycol components, and the copolymerization ratio of diethylene glycol is 2.0 to 4.0% by weight of the polyester copolymer. A method for producing a polyester copolymer for bottles, wherein substantially non-crystalline germanium dioxide is used as a polymerization catalyst, and the timing of adding the polymerization catalyst is at a point when the esterification rate reaches 90% or more. Manufacturing method.