JP2013127084A - Polyethylene terephthalate composition and method for producing the same and film thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene terephthalate composition good in polymerization reactivity and hydrolysis resistance.SOLUTION: The polyethylene terephthalate composition comprises a polyethylene terephthalate containing 0.1-5.0 mol/t of a buffering agent, wherein the polyethylene terephthalate is such as to be 20 eq/t in the number of terminal carboxyl groups, 0.6-1.0 in intrinsic viscosity, 0.1-10 mol/t in alkali metal content, and 0.01 wt.% in deposits amount attributable to catalyst residues.

Description

  The present invention relates to a polyester composition having good hydrolysis resistance, a method for producing the same, and a film.

Polyethylene terephthalate is excellent in mechanical properties, thermal properties, chemical resistance, electrical properties, and moldability, and is used in various applications.
However, since the mechanical properties of polyethylene terephthalate decrease due to hydrolysis, various studies have been made to suppress hydrolysis when used over a long period of time or when used in a damp state.

  For example, Patent Document 1 describes a polyester containing a specific amount of alkali metal, alkaline earth metal, and phosphorus and containing internally precipitated particles due to catalyst residues. However, since the phosphorus compound becomes internal particles, Insufficient hydrolyzability.

  Patent Document 2 discloses a technique for improving the hydrolysis resistance of polyester by using an epoxy compound. However, the epoxy compound is gelled during material recycling and causes molding defects, and it is necessary to remove it during chemical recycling because it is likely to become a foreign object during melt molding. This is also not preferable.

  Patent Document 3 describes a method for producing a polyester using a polycondensation catalyst comprising an alkali metal phosphate and a titanium compound. However, since the alkali metal phosphate contained in the polycondensation catalyst acts with the titanium compound, a sufficient effect cannot be obtained in hydrolysis resistance.

  Patent Document 4 describes a method for producing a polyester having excellent transparency in which the contents of an antimony compound, an alkali metal compound, and a phosphorus compound are defined. However, since phosphorus compounds and alkali metal compounds are consumed in the generated internal particles in a small amount, the heat resistance is good, but sufficient hydrolysis resistance cannot be obtained.

JP 60-31526 A JP-A-9-227767 (Claims 1, 3, 4) JP 2000-143789 A (Claims 1 and 10 to 12) JP-A-61-78828 (Claim 1)

  An object of the present invention is to eliminate these conventional drawbacks and to provide a polyester composition excellent in hydrolysis resistance, heat resistance and mechanical properties.

A polyethylene terephthalate containing 0.1 to 5.0 mol / t of a buffer derived from the compound represented by the following formula (I), wherein the polyethylene terephthalate has a carboxylic acid terminal group number of 20 eq / t or less and an intrinsic viscosity of 0.8. A germanium compound or titanium compound derived from a polycondensation catalyst having a content of 6 to 1.0, potassium and / or sodium of 0.1 to 10 mol / t, 50 to 300 ppm as a germanium element, or 0.1 as a titanium element It is achieved by a polyethylene terephthalate composition containing ˜20 ppm and containing 0.001% by weight or less of precipitates due to catalyst residues.
POxHyMz (I)
(Here, x is an integer of 2 to 4, y is 1 or 2, z is 1 or 2, and M is potassium and / or sodium.)

According to the present invention, it is possible to provide a polyethylene terephthalate composition having excellent hydrolysis resistance while maintaining polymerization reactivity. Moreover, by using the composition of the present invention as a biaxially stretched film, it can be provided for uses such as magnetic materials, electrical materials such as capacitors, and packaging.

The polyethylene terephthalate composition of the present invention is a polyethylene terephthalate containing 0.1 to 5.0 mol / t of a buffer, and the polyethylene terephthalate has a carboxylic acid terminal group number of 20 eq / t or less and an intrinsic viscosity of 0.6 to 1.0.

  In the polyethylene terephthalate of the present invention, it is necessary from the viewpoint of hydrolysis resistance and heat resistance that 95 mol% or more of the acid component is a terephthalic acid component and 95 mol% or more of the glycol component is an ethylene glycol component. When the copolymerization component exceeds 5 mol%, the heat resistance is lowered due to the melting point drop, and the hydrolysis resistance is lowered due to the crystallinity drop.

  The number of carboxylic acid end groups of the polyethylene terephthalate needs to be 20 eq / t or less, and more preferably 15 eq / t or less. When it exceeds 20 eq / t, hydrolysis is promoted by the catalytic action of the carboxylic acid end group, which causes a decrease in mechanical properties. In order to reduce the number of carboxylic acid end groups to 20 eq / t or less, a buffer is added between the end of the transesterification or esterification reaction and the beginning of the polycondensation reaction (inherent viscosity is less than 0.3). A method of phase polymerization or the like can also be employed.

The intrinsic viscosity needs to be 0.6 to 1.0, and more preferably 0.65 to 0.8. When the intrinsic viscosity is less than 0.6, the molecular weight of polyethylene terephthalate may be too low to obtain sufficient mechanical properties. If the intrinsic viscosity exceeds 1.0, the polymerization time becomes long, which is disadvantageous in terms of cost. To achieve the target intrinsic viscosity, when the melt viscosity reaches a predetermined melt viscosity, discharge, stranding and cutting are performed to form chips, and chips are formed once with an intrinsic viscosity lower than the target. Although there is a method of performing polymerization, when the target intrinsic viscosity is 0.7 to 1.0, a method of performing solid phase polymerization is preferable in that the amount of carboxylic acid end groups can be reduced.
Further, the content of diethylene glycol as a by-product is preferably less than 2.0% by weight from the viewpoint of heat resistance and hydrolysis resistance, and more preferably less than 1.0% by weight.

It is necessary from the viewpoint of heat resistance and hydrolysis resistance that the content of alkali metal contained in the polyethylene terephthalate composition of the present invention is 0.1 to 10 mol / t. If it is less than 0.1 mol / t, sufficient hydrolysis resistance and a reduction effect of carboxylic acid end groups cannot be obtained. If it exceeds 10 mol / t, there is little improvement effect on hydrolysis resistance with respect to the content, and heat resistance is reduced. Cause.
Further, it is preferable from the viewpoint of heat resistance and hydrolysis resistance that the total amount of the alkali metal or 95 mol% or more (relative to the total amount of the alkali metal) is derived from the buffer.

  The buffer of the present invention is a substance that is soluble in ethylene glycol and dissociates to exhibit ionicity. Further, the buffering agent is preferably an alkali metal salt from the viewpoint of polymerization reactivity and hydrolysis resistance. For example, phthalic acid, citric acid, carbonic acid, lactic acid, tartaric acid, phosphoric acid, phosphorous acid, hypophosphorous acid And alkali metal salts with compounds such as polyacrylic acid. Among them, it is preferable that the alkali metal is potassium or sodium from the point that precipitates due to the catalyst residue are not easily generated. Specifically, potassium hydrogen phthalate, sodium dihydrogen citrate, disodium hydrogen citrate, citric acid Potassium dihydrogen, dipotassium citrate, sodium carbonate, sodium tartrate, potassium tartrate, sodium lactate, potassium lactate, sodium bicarbonate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, diphosphate phosphate Examples thereof include sodium hydrogen, sodium hydrogen phosphite, potassium hydrogen phosphite, sodium hypophosphite, potassium hypophosphite, and sodium polyacrylate.

In addition, an alkali metal salt represented by the following formula is preferable from the viewpoint of heat resistance and polymerization reactivity, and further, the alkali metal is sodium and / or potassium, polymerization reactivity, heat resistance, hydrolysis resistance. In particular, phosphoric acid and sodium and / or potassium metal salts are preferred in view of polymerization reactivity and hydrolysis resistance.
POxHyMz (I)
(Here, x is an integer of 2 to 4, y is 1 or 2, z is 1 or 2, and M is potassium and / or sodium.)
The content of the buffering agent needs to be 0.1 to 5.0 mol / t, more preferably 0.3 to 3.0 mol / t, with respect to the polyethylene terephthalate composition. When the amount is less than 0.1 mol / t, sufficient hydrolysis resistance cannot be obtained, and hydrolysis proceeds gradually during long-term use, causing deterioration of mechanical properties. If it exceeds 5.0 mol / t, the decomposition reaction is promoted by excess alkali metal, which causes a decrease in molecular weight and a decrease in mechanical properties.

  Such a buffering agent can be added at any time from the end of the esterification reaction or transesterification reaction to the beginning of the polycondensation reaction (inherent viscosity is less than 0.3). . The buffering agent may be added in any form such as an ethylene glycol solution or powder, but it is preferably added as an ethylene glycol solution, and the concentration is diluted to 10% by weight or less in some cases. When added, the buffer agent is less likely to adhere to the vicinity of the addition port, which is preferable in terms of the addition error and the reactivity.

  As the polycondensation catalyst of the present application, conventional antimony compounds, germanium compounds, and titanium compounds can be used. In the case of using an antimony compound and / or a germanium compound, the antimony element and germanium element are preferably 50 ppm to 300 ppm in terms of polycondensation reactivity and solid phase polymerization reactivity, and more preferably 50 to 200 ppm. Is preferable from the viewpoint of heat resistance and hydrolysis resistance. If it exceeds 300 ppm, the polycondensation reactivity and solid-phase polymerization reactivity will improve, but the decomposition reaction during remelting will also be accelerated, leading to an increase in carboxylic acid end groups and a decrease in heat resistance and hydrolysis resistance. It may become. Examples of the antimony compound and the germanium compound that are preferably used include antimony pentoxide, antimony trioxide, and germanium dioxide, which can be used according to the purpose. For example, the best color tone is the germanium compound, and the solid-phase polymerization reactivity is the antimony compound. In consideration of the environment, the titanium catalyst is polycondensed when manufactured in a non-antimony system. This is preferable in that the reactivity of the reaction and solid phase polymerization is improved.

  When a titanium compound is used as the polycondensation catalyst, 0.1 to 20 ppm as the titanium element is preferable from the viewpoints of polycondensation reactivity and solid phase polymerization reactivity. If the amount of titanium element exceeds 20 ppm, the polycondensation reactivity and the solid-phase polymerization reactivity are improved, but this may cause a decrease in heat resistance, hydrolysis resistance, and color tone. Examples of the titanium catalyst used as the polycondensation catalyst include alkoxides such as tetrabutoxy titanate and tetraisopropyl titanate, and titanium chelate compounds of titanium and lactic acid, citric acid, etc. Among them, titanium chelate compounds Is preferable from the viewpoint of heat resistance, hydrolysis resistance, and color tone.

When a titanium compound is used as a polycondensation catalyst, buffering agents include potassium hydrogen phthalate, disodium hydrogen citrate, sodium dihydrogen citrate, potassium dihydrogen citrate, dipotassium hydrogen citrate, sodium carbonate, sodium tartrate, tartaric acid Use of a non-phosphorus buffer such as potassium, sodium lactate, potassium lactate or sodium hydrogen carbonate is preferred for improving hydrolysis resistance without impairing polycondensation reactivity and solid phase polymerization reactivity. In addition, when a compound of the following formula (I) is used as a buffering agent, the polycondensation reactivity and the solid-state polymerization reactivity can be improved by adding the buffering agent 5 minutes or more before the titanium compound is added or after 5 minutes or more. It is preferable in order to improve the hydrolysis resistance without impairing.
POxHyMz (I)
(Here, x is an integer of 2 to 4, y is 1 or 2, z is 1 or 2, and M is potassium and / or sodium.)
The deposit by the catalyst residue of the present invention is a product in which the catalyst residue is deposited in the course of the polymerization reaction to form particles or foreign matters. Specifically, the precipitate is detected as an insoluble when the polymer is dissolved in orthochlorophenol. It is a compound. The content of the precipitate due to the catalyst residue is required to be 0.01% by weight or less, more preferably 0.001% by weight or less based on the polyethylene terephthalate composition. If the deposit due to the catalyst residue exceeds 0.01% by weight, it becomes a defect such as fish eye when it is formed into a film, and alkali metal is taken into the precipitate during the precipitation process of the catalyst residue, resulting in hydrolysis resistance. May decrease.

The method for producing the polyethylene terephthalate composition of the present application will be described in detail below.
The polyethylene terephthalate composition of the present application can be produced by either the DMT method using dimethyl terephthalate as a raw material or the direct weight method using terephthalic acid as a raw material. This is preferable because the amount of the catalyst metal is small and the decomposition reaction due to the catalyst residue hardly occurs.

In the case of the direct polymerization method, the esterification reaction and polycondensation reaction can be carried out by conventional methods. During the period from the end of the esterification reaction to the initial stage of the polycondensation reaction (with an intrinsic viscosity of less than 0.3), Antimony compounds, germanium compounds, or titanium compounds and buffering agents can be added as phosphoric acid, phosphoric acid ester, polycondensation catalyst, respectively. The order of addition is as follows: heat stabilizer, polycondensation catalyst, buffering agent. It is preferable to leave the addition interval at least 5 minutes from the viewpoints of polycondensation reactivity and hydrolysis resistance.
In addition, as a technique for reducing the carboxylic acid end group, a trace amount of an alkali metal compound such as potassium hydroxide is added during the initial period to the middle period of the esterification reaction, or before the start of the transesterification reaction and during the initial stage of the reaction. In order to improve the application characteristics, a small amount of magnesium compound such as magnesium acetate can be added from the end of the esterification reaction to the beginning of the polycondensation reaction or before the start of the transesterification reaction.

  The polyethylene terephthalate composition of the present invention is melt-kneaded with polyetherimide and a vent type twin screw extruder to form a polyester composition having a glass transition point of 90 to 120 ° C., so that higher heat resistance and dimensional stability. It can be applied to special applications that require high rigidity.

  The polyetherimide is not particularly limited as long as it is compatible with polyethylene terephthalate, but from the viewpoint of compatibility, 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride and A condensate with m-phenylenediamine is preferred.

The mixing ratio of the polyetherimide and the polyethylene terephthalate composition is preferably 1 to 50:99 to 50 (weight ratio) from the viewpoint of compatibility, heat resistance, and high rigidity, and more preferably 1 to 20:99 to 80. It is preferable to reduce the foreign matter.
The polyethylene terephthalate composition and the polyester composition thus obtained can be dried, extruded with a normal extruder and a T-die, and biaxially stretched. At this time, it is better that the time from the supply of the chip to the extruder to the extrusion from the T die is as short as possible, and as a guideline, it is preferable to set it to 30 minutes or less from the viewpoint of suppressing an increase in carboxylic acid end groups.

(A. Intrinsic viscosity)
It measured at 25 degreeC using the o-chlorophenol solvent.

(B. Determination of phosphorus content in polymer)
The measurement was performed using a fluorescent X-ray analyzer (model number: 3270) manufactured by Rigaku Corporation.

(C. Determination of alkali metal content in polymer)
Quantification was performed by atomic absorption analysis (manufactured by Hitachi, Ltd .: polarized Zeeman atomic absorption photometer 180-80, frame: acetylene-air).

(D. Carboxylic acid end group amount)
Measured by the method of Malice. (Reference M. J. Malice, F. Huizinga. Anal. Chim. Acta, 22 363 (1960)).

(E. Measurement of glass transition point)
Measurement was performed under the following conditions using a temperature modulated DSC manufactured by TA Instrument.
Heating temperature: 270-570K (RCS cooling method)
Temperature calibration: Melting point of high purity indium and tin Temperature modulation amplitude: ± 1K
Temperature modulation period: 60 seconds Temperature step: 5K
Sample weight: 5mg
Sample container: Aluminum open container (22 mg)
Reference container: Aluminum open container (18mg)
The glass transition point was calculated from the following formula.
Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature / 2).

(F. Evaluation of hydrolysis resistance)
The polymer which had been vacuum-dried at 160 ° C. for 8 hours was treated for 4 hours at 155 ° C. in saturated steam, and then the intrinsic viscosity and carboxylic acid end groups were measured.
For the non-solid phase polymerized product, the carboxylic acid end group amount after treatment was 100 eq / t or less, and the hydrolysis resistance index calculated by the following formula was 0.65 or less.
Moreover, about the solid-phase polymerization product, the carboxylic acid terminal group amount was 50 eq / t or less, and the hydrolysis resistance index calculated by the following formula was 0.30 or less.
Hydrolysis resistance index = 0.27 (1 / [ηt] 1.3-1 / [η] 1.3)
[Η]: Intrinsic viscosity before treatment [ηt]: Intrinsic viscosity after treatment.

(G. Evaluation of polymerization reactivity)
The time until reaching the intrinsic viscosity of 0.65 was evaluated as follows in comparison with the blank (Reference Example 2), and ◎ and ○ were regarded as acceptable.
◎ ・ ・ ・ Delay is less than 15 minutes ○ ・ ・ ・ Delay is 15 minutes or more and less than 30 minutes Δ ・ ・ ・ Delay is 30 minutes or more and less than 45 ×× Delay is 45 minutes or more

(H. Determination of precipitates from catalyst residues)
100 g of a polyethylene terephthalate composition is dissolved in 1 L of orthochlorophenol at 100 ° C. for 10 hours and centrifuged.
When a few drops of acetone are added to the orthochlorophenol solution after centrifugation and the solution becomes cloudy, the insoluble matter is again dissolved in 1 L of orthochlorophenol at 100 ° C. for 10 hours and centrifuged.
This operation is repeated until the orthochlorophenol after centrifugation does not become cloudy even when acetone is added.
If it is confirmed that the orthochlorophenol after centrifugation does not become cloudy even when acetone is added, the insoluble matter at this time is washed with acetone, centrifuged, dried, and quantified.

(I. Measurement of Young's modulus)
According to the method prescribed | regulated to ASTM-d882, it measured on condition of the following using the Instron type tensile tester.
Measuring device: Orientec Co., Ltd. film strength measuring device
“Tensilon AMF / RTA-100”
Sample size: width 10mm x test length 100mm
Tensile speed: 200 mm / min Measurement environment: 23 ° C., 65% RH.

(Reference Example 1)
Catalyst A. Citric acid chelate titanium compound synthesis method Citric acid monohydrate (532 g, 2.52 mol) was dissolved in warm water (371 g) in a 3 L flask equipped with a stirrer, a condenser and a thermometer. To this stirred solution was slowly added titanium tetraisopropoxide (288 g, 1.00 mol) from the addition funnel. The mixture was heated to reflux for 1 hour to produce a cloudy solution from which the isopropanol / water mixture was distilled under reduced pressure. The product was cooled to a temperature below 70 ° C., and a 32 wt / wt% aqueous solution of NaOH (380 g, 3.04 mol) was slowly added via a dropping funnel to the stirred solution. The resulting product was filtered and then mixed with ethylene glycol (504 g, 80 mol) and heated under reduced pressure to remove isopropanol / water and a slightly cloudy light yellow product (Ti content 3 .85% by weight).

(Reference Example 2)
66 parts by weight of bishydroxyethyl terephthalic acid (reagent: manufactured by Aldrich) was dissolved at 250 ° C. in a nitrogen atmosphere, and a slurry of 43.2 parts by weight of high-purity terephthalic acid and 18.6 parts by weight of ethylene glycol was taken over 2.5 hours. The esterification reaction was completed. After completion of the esterification reaction, 0.01 parts by weight of trimethyl phosphate was added and stirred for 5 minutes, 0.05 parts by weight of magnesium acetate and 0.12 parts by weight of antimony trioxide were added, the temperature was raised to 290 ° C., and the pressure was reduced. Finally, a polycondensation reaction was performed at a vacuum of 133 Pa or less to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65 and a carboxylic acid end group of 29.3 eq / t.

(Reference Example 3)
The polyethylene terephthalate composition obtained in Reference Example 2 was vacuum-dried at 160 ° C. for 4 hours, and then subjected to a solid-phase polymerization reaction at 220 ° C. for 8 hours and a vacuum degree of 133 Pa or less to obtain a polyethylene terephthalate composition having an intrinsic viscosity of 0.85. I got a thing.

Reference Example 7
66 parts by weight of bishydroxyethyl terephthalic acid (reagent: manufactured by Aldrich) was dissolved at 250 ° C. in a nitrogen atmosphere, and a slurry of 43.2 parts by weight of high-purity terephthalic acid and 18.6 parts by weight of ethylene glycol was taken over 2.5 hours. The esterification reaction was completed. After completion of the esterification reaction, 0.01 part by weight of trimethyl phosphate was added and stirred for 5 minutes, 0.05 part by weight of magnesium acetate and 0.12 part by weight of antimony trioxide were added and stirred for 5 minutes. Hydrogen phosphate as a buffering agent 0.013 part by weight of dipotassium (equivalent to 0.75 mol / t) was added, the temperature was increased to 290 ° C., the pressure was reduced, and finally a polycondensation reaction was performed at a vacuum of 133 Pa or less, and an intrinsic viscosity of 0.65, Polyethylene terephthalate having a carboxylic acid end group of 16.2 eq / t was obtained.

Example 2
Polyethylene t-rephthalate was obtained in the same manner as in Reference Example 7 except that antimony trioxide was changed to 0.017 parts by weight of germanium dioxide.

Reference example 4
A polyethylene terephthalate composition was obtained in the same manner as in Reference Example 7 except that dipotassium hydrogen phosphate was changed to 0.034 parts by weight of potassium dihydrogen citrate (equivalent to 1.5 mol / t).

Reference Example 5
A polyethylene terephthalate composition was obtained in the same manner as in Example 1 except that the antimony trioxide was 0.013 part by weight of catalyst A.

Reference Example 8
A polyethylene terephthalate composition was obtained in the same manner as in Reference Example 7 except that the amount of dipotassium hydrogen phosphate added was 0.026 parts by weight (equivalent to 1.5 mol / t).
Reference Example 6 A polyethylene terephthalate composition was obtained in the same manner as in Example 1 except that dipotassium hydrogen phosphate was changed to 0.007 parts by weight of phosphoric acid and 0.008 parts by weight of potassium hydroxide (equivalent to 1.5 mol / t). It was.

Reference Example 9
A polyethylene terephthalate composition was obtained in the same manner as in Reference Example 7 except that dipotassium hydrogen phosphate was changed to 0.012 double dragon part (corresponding to 0.75 mol / t) of sodium dihydrogen phosphate dihydrate.

Reference Example 10
Except for using two kinds of compounds as a buffering agent, 0.013 part by weight of dipotassium hydrogen phosphate (equivalent to 0.75 mol / t) and sodium dihydrogen phosphate dihydrate 0.012 (equivalent to 0.75 mol / t). Obtained a polyethylene terephthalate composition in the same manner as in Reference Example 7.

Comparative Example 1
A polyethylene terephthalate composition was obtained in the same manner as in Reference Example 7 except that dipotassium hydrogen phosphate was changed to 0.01 part by weight of trimethyl phosphate (corresponding to 0.75 mol / t).

Comparative Example 2
A polycondensation reaction was carried out in the same manner as in Reference Example 4 except that potassium hydrogen citrate was changed to 0.090 parts by weight of potassium phosphate (corresponding to 4.25 mol / t), but the degree of polymerization was not increased and a polymer was obtained. There wasn't.

Reference Example 11
The polyethylene terephthalate composition obtained in Reference Example 7 was vacuum-dried at 160 ° C. for 4 hours, and then subjected to a solid-phase polymerization reaction at 220 ° C. for 8 hours and a vacuum degree of 133 Pa or less to obtain a polyethylene terephthalate composition having an intrinsic viscosity of 0.85. I got a thing.
The polyethylene terephthalate composition after solid phase polymerization is supplied to a single screw extruder and melt-extruded to a mirror drum (surface temperature 25 ° C) with a T-die, 3.5 times at 90 ° C in the vertical direction and 95 ° C in the width direction. After stretching 4.0 times, heat setting was performed at 200 ° C. for 3 seconds to obtain a biaxially stretched film.

Reference Example 12
The polyethylene terephthalate composition after solid phase polymerization obtained in Reference Example 11 is the outermost layer (A layer), the polyethylene terephthalate composition of Reference Example 2 is the intermediate layer (B layer), and an A / B / A laminated film A biaxially stretched film was obtained in the same manner as in Example 7 except that.

Reference Example 13
90 parts by weight of the polyethylene terephthalate composition obtained in Reference Example 7 and 10 parts by weight of polyetherimide (“Ultem” 1010: manufactured by General Electric) were supplied to a vented twin screw extruder heated to 280 ° C., and the shear rate Polyester A was obtained by melt extrusion at 100 sec-1 and a residence time of 1 minute.
The obtained polyester A was vacuum-dried at 160 ° C. for 4 hours, supplied to a single screw extruder, melt-extruded to a mirror drum (surface temperature 25 ° C.) with a T-die, and 3.0 times at 110 ° C. in the longitudinal direction. The film was stretched 4.5 times at 100 ° C. in the width direction, and again stretched 1.5 times at 150 ° C. in the longitudinal direction and then 1.5 times at 210 ° C. in the width direction to obtain a biaxially stretched film.

Reference Example 14
In the same manner as in Example 11, 90 parts by weight of the polyethylene terephthalate composition after solid phase polymerization obtained in Reference Example 11 and 10 parts by weight of polyetherimide (“Ultem” 1010: manufactured by General Electric Co.) were used. An axially stretched film was obtained.

Reference Example 15
As a buffering agent, two types of compounds, 0.026 part by weight of dipotassium hydrogen phosphate (equivalent to 1.50 mol / t) and sodium dihydrogen phosphate dihydrate 0.024 (equivalent to 1.50 mol / t), A polyethylene terephthalate composition was obtained in the same manner as in Example 1 except that 0.005 parts by weight of phosphoric acid was used instead of trimethyl acid.

Claims (8)

A polyethylene terephthalate containing 0.1 to 5.0 mol / t of a buffer derived from the compound represented by the following formula (I), wherein the polyethylene terephthalate has a carboxylic acid terminal group number of 20 eq / t or less and an intrinsic viscosity of 0.8. A germanium compound or titanium compound derived from a polycondensation catalyst having a content of 6 to 1.0, potassium and / or sodium of 0.1 to 10 mol / t, 50 to 300 ppm as a germanium element, or 0.1 as a titanium element A polyethylene terephthalate composition containing ˜20 ppm and containing 0.001% by weight or less of deposits due to catalyst residues.
POxHyMz (I)
(Here, x is an integer of 2 to 4, y is 1 or 2, z is 1 or 2, and M is potassium and / or sodium.)   A polyester composition, which is a polyester composition having a glass transition point of 90 to 120 ° C. containing 50 to 99% by weight of the polyethylene terephthalate composition according to claim 1 and 1 to 50% by weight of polyetherimide. In a method for producing polyethylene terephthalate in which terephthalic acid or dimethyl terephthalate and ethylene glycol are subjected to esterification reaction or transesterification reaction, and then polycondensation reaction is performed, a germanium compound or a titanium compound derived from a polycondensation catalyst is used as a germanium element in an amount of 50 to 50 300 ppm, or 0.1 to 20 ppm as titanium element, and 0.1 to 5. 5 of a buffering agent represented by the following formula (I) between the end of the esterification reaction or transesterification reaction and the beginning of the polycondensation reaction. 0 mol / t addition, The manufacturing method of the polyethylene terephthalate composition characterized by the above-mentioned.
POxHyMz (I)
(Where x is an integer of 2 to 4, y is 1 or 2, z is 1 or 2, and M is potassium and / or sodium.)   The titanium compound is added as a titanium element as a polycondensation catalyst in an amount of 0.1 to 20 ppm, and a buffering agent is added before or after the addition of the titanium compound at intervals of 5 minutes or more. The manufacturing method of the polyethylene terephthalate composition of description. A polyester composition characterized by melting and kneading the polyethylene terephthalate composition obtained by the production method according to claim 3 or 4 and a polyetherimide at a weight ratio of 99 to 50: 1 to 50. Production method.   The biaxially stretched film which consists of a polyethylene terephthalate composition obtained by the manufacturing method of any one of Claims 3-5, or a polyester composition.   A multi-layered biaxially stretched film comprising at least the outermost layer of the film according to claim 6.   A biaxially stretched polyester film, wherein the biaxially stretched film according to claim 6 or 7 is used for electrolysis.