WO2014021323A1

WO2014021323A1 - Manufacturing method for polyester film, polyester film, protective sheet for solar cell, and solar cell module

Info

Publication number: WO2014021323A1
Application number: PCT/JP2013/070616
Authority: WO
Inventors: 崇喜 ▲桑▼原
Original assignee: 富士フイルム株式会社
Priority date: 2012-07-31
Filing date: 2013-07-30
Publication date: 2014-02-06
Also published as: JP5770693B2; JP2014028898A

Abstract

A starting material, which comprises: 5 to 50 parts by mass of a recycle polyester material in which a first carbodiimide compound is deactivated by bringing an inert gas or air with a dew point of -25°C or below and an isocyanate concentration of 0.01 ppm to 100 ppm into contact with a recycle polyester material including the first carbodiimide compound and then performing drying; 50 to 95 parts by mass of a polyester resin; and a second carbodiimide compound, is subjected to melt extrusion which involves performing melt-kneading and extruding a molten resin using an extruder, and then moulding is performed in order to form a film shape, and accordingly a polyester film having the total content of a carbodiimide compound of 0.1 to 2.0 mass% is formed.

Description

Method for producing polyester film, polyester film, protective sheet for solar cell, and solar cell module

The present invention relates to a method for producing a polyester film, a polyester film, a solar cell protective sheet, and a solar cell module.

In recent years, resin materials such as polyester have been used for protective sheets disposed on the side opposite to the sunlight incident side of the solar cell module. Polyester usually has many carboxyl groups and hydroxyl groups on its surface, and in an environment where moisture exists, the polyester tends to undergo hydrolysis and tends to deteriorate over time. For this reason, polyesters used in solar cell modules and the like that are constantly exposed to wind and rain such as outdoors are required to have reduced hydrolyzability.
For example, Japanese Patent Laid-Open No. 5-237927 discloses a polyester chip having a moisture content of 0.01 to 0.10% and an intrinsic viscosity (IV) of 0.50 to 0.90 with air having a dew point of −12 ° C. or less. There is disclosed a method for producing a polyester film which is dried by purging with an active gas so that the moisture content of the chip is maintained at 0.01 to 0.10%, melt-extruded, and biaxially stretched in the longitudinal direction and the width direction.

Japanese Patent Application Publication No. 2004-530000 discloses a method for lowering the Tg of a poly (ethylene terephthalate) homopolymer or copolymer, in which (a) the poly (trimethylene terephthalate) homopolymer or copolymer is converted into a crystallized poly Adding to (ethylene terephthalate) homopolymer or copolymer to form a blend; and (b) dew point at a temperature in the range of about 120 ° C. to about 130 ° C. for at least about 6 hours or until sufficient drying has occurred. Drying the blend by exposing the blend to a flow of at least 0.028 m ³ / min (1 ft ³ / min) of dry air below 5 ° C. (−5 ° F.); (c) melting the blend Poly blended and having a lower Tg than the poly (ethylene terephthalate) of step (a) Method comprising the step of forming the over is disclosed.

Japanese Patent Application Laid-Open No. 2010-235824 uses a carbodiimide compound as an end-capping agent when melt-extruding a polyester resin, and the amount of isocyanate-based gas generated at a temperature of 300 ° C. for 30 minutes is 0 to 0.05. Biaxially oriented polyester films that are weight percent are disclosed.

The carbodiimide compound exhibits a sealing effect in a relatively small amount, and the unreacted component exhibits a high sealing reaction (ambushing effect) even after film formation. When manufacturing a polyester film by adding a carbodiimide compound as an end-capping agent, the part that cannot be used as a product is cut out and collected, and when this is used as a part of the raw material as a recycled polyester material, Since unreacted carbodiimide compounds remain, the resulting film will gel with higher molecular weight as the number of recycles increases, and it will become colored (decrease in transparency) and stabilize the product quality. There is a problem such as not.

For example, although the method of reducing the compounding quantity of recycled polyester material can be considered, supply of the raw material by a feeder becomes unstable.
Moreover, although the method of using together the recycled polyester material containing terminal blocker and the recycled polyester material which does not contain terminal blocker can be considered, the recycled polyester material which does not contain terminal blocker is usually intrinsic viscosity ( IV) is high and the amount of terminal carboxyl groups (AV) is high, so that the physical properties of the produced polyester film are likely to vary.
Although a method of reducing the carbodiimide compound remaining in the recycled polyester material by vacuum drying is conceivable, a separate step of vacuum drying the recycled polyester material is required, resulting in an increase in manufacturing cost.

The present invention relates to a method for producing a polyester film, in which the generation of a gelled product is suppressed and excellent in hydrolysis resistance, using a recycled polyester material at a low cost, as well as a polyester film excellent in weather resistance, and protection for solar cells. It aims at providing a sheet | seat and a solar cell module.

In order to achieve the above object, the following invention is provided.
<1> The recycled polyester material containing the first carbodiimide compound is dried by contacting with air or an inert gas having a dew point of −25 ° C. or less and an isocyanate concentration of 0.01 ppm to 100 ppm. A recycled material drying step for deactivating the first carbodiimide compound;
A melt extrusion process in which 50 to 95 parts by mass of a polyester resin, 5 to 50 parts by mass of the dried recycled polyester material, and a raw material containing a second carbodiimide compound are melt-kneaded by an extruder to extrude the molten resin;
A film forming step of forming a polyester film having a total content of carbodiimide compounds of 0.1 to 2.0% by mass by molding the molten resin extruded from the extruder into a film;
The manufacturing method of the polyester film which has this.
<2> The method for producing a polyester film according to <1>, wherein the recycled polyester material is dried at 135 to 180 ° C. in the recycled material drying step.
<3> The amount of terminal carboxyl groups (AV) of the recycled polyester material is 3 to 20 equivalents / ton, and the amount of terminal carboxyl groups (AV) of the polyester resin is 3 to 55 equivalents / ton <1> or < The manufacturing method of the polyester film of 2>.
<4> At least one of the polyester resin and the recycled polyester material has a structure derived from 1,4-cyclohexanedimethanol in an amount of 0.1 to 20 mol% or 80 to 100 mol based on the total structure derived from the diol component. %. The method for producing a polyester film according to any one of <1> to <3>, which contains 1,4-cyclohexanedimethanol-based polyester.
<5> At least one of the first carbodiimide compound contained in the recycled polyester material and the second carbodiimide compound contained in the raw material has one carbodiimide group, and the first nitrogen and the second nitrogen are The method for producing a polyester film according to any one of <1> to <4>, which is a cyclic carbodiimide compound containing a cyclic structure bonded by a bonding group.
<6> The method for producing a polyester film according to <5>, wherein the cyclic carbodiimide compound is at least one selected from compounds represented by the following formulas (2) to (4).

Wherein (2), Q _a is an aliphatic group, an alicyclic group, an aromatic group or a divalent linking group which is a combination of these, it may contain a heteroatom.

Wherein (3), Q _b is an aliphatic group, an alicyclic group, an aromatic group or a trivalent linking group combinations thereof, and may contain a hetero atom. Y represents a carrier supporting a cyclic structure.

In formula (4), Q _c is any one tetravalent linking group selected from the group consisting of an aliphatic group, an alicyclic group, and an aromatic group, or an aliphatic group, an alicyclic group, And a tetravalent linking group that is a combination of two or more groups selected from the group consisting of aromatic groups, and may further have a heteroatom. Z ¹ and Z ² each independently represent a carrier carrying a cyclic structure, and may be bonded to each other to form a cyclic structure.
<7> A polyester film produced by the method for producing a polyester film according to any one of <1> to <6>.
<8> A solar cell protective sheet comprising the polyester film according to <7>.
<9> A solar cell module comprising the solar cell protective sheet according to <8>.

ADVANTAGE OF THE INVENTION According to this invention, the generation | occurrence | production of a gelled substance is suppressed, the method of manufacturing the polyester film excellent in hydrolysis resistance at low cost using a recycled polyester material, the polyester film excellent in a weather resistance, and a solar cell A protective sheet and a solar cell module are provided.

It is the schematic which shows the structural example of the twin-screw extruder for enforcing the manufacturing method of the polyester film which concerns on this invention. It is a figure which shows an example of the flow which enforces the manufacturing method of the polyester film which concerns on this invention.

Hereinafter, the method for producing the polyester film of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

The present inventor has conceived that it is effective to preferentially deactivate the carbodiimide compound remaining in the recycled polyester material under specific drying conditions.
As a method for deactivating the carbodiimide compound in the recycled polyester material, it may be possible to treat with wet heat, light, alkali, etc., but the polyester resin itself may be decomposed. However, since the hydrolysis rate of the carbodiimide compound is much higher than the hydrolysis rate of the polyester resin, the carbodiimide compound having a high hydrolysis rate can be preferentially decomposed by utilizing the difference in hydrolysis rate. Similarly, the carbodiimide compound in the recycled polyester material can be more effectively deactivated (decomposed) by using an isocyanate gas having an effect of preferentially deactivating the carbodiimide compound.

And this inventor mix | blends the recycled polyester material which deactivated the 1st carbodiimide compound by the said specific drying conditions, the polyester resin obtained by superposition | polymerization, and a 2nd carbodiimide compound in a specific quantity, respectively. If a polyester film having a total carbodiimide compound content of 0.1 to 2.0% by mass is formed by melt extrusion and film formation, the generation of gelled products is suppressed even when recycling is repeated, and the It has been found that a polyester film excellent in hydrolyzability can be produced at low cost.

That is, the method for producing a polyester film of the present invention includes a recycled polyester material containing a first carbodiimide compound, air or an inert gas having a dew point of −25 ° C. or lower and an isocyanate concentration of 0.01 ppm to 100 ppm. A recycled material drying step in which the first carbodiimide compound is deactivated by contacting and drying, a polyester resin in an amount of 50 to 95 parts by mass, a dried recycled polyester material in an amount of 5 to 50 parts by mass, and a second A melt extrusion process in which a raw material containing a carbodiimide compound is melt-kneaded by an extruder to extrude a molten resin, and the molten resin extruded from the extruder is formed into a film to have a total content of carbodiimide compounds of 0.1 to Film forming to form 2.0% by mass polyester film Has a degree, the.

<Recycled material drying process>
In the present invention, a recycled polyester material containing a carbodiimide compound (hereinafter sometimes simply referred to as “recycled material”) is used as a part of the raw material.
Recycled polyester materials containing carbodiimide compounds include, for example, product films such as parts that have a relatively large thickness or parts that are clipped during lateral stretching when manufacturing polyester films that use carbodiimide compounds as end-capping agents. Because it cannot be used, a polyester piece that has been excised and recovered can be used.

Recycled polyester material obtained in the process of producing a polyester film using a carbodiimide compound is simply dried and mixed with a polyester resin and a carbodiimide compound in the production process of a new polyester film. A carbodiimide compound also functions as a terminal blocking agent. Therefore, as described above, in the obtained film, as the number of times of recycling increases, the generation of high molecular weight substances due to the carbodiimide compound increases, causing problems such as gelation, coloring, and unstable product quality. is there.

On the other hand, in the present invention, the recycled polyester material containing a carbodiimide compound is recycled by bringing it into contact with air or an inert gas having a dew point of −25 ° C. or less and an isocyanate concentration of 0.01 ppm to 100 ppm and drying it. The carbodiimide compound contained in the material is deactivated.

When the dew point in the drying process of the recycled polyester is −25 ° C. or less, the moisture content of the recycled material is sufficiently lowered, and hydrolysis of the polyester resin is suppressed. From the viewpoint of suppressing degradation of hydrolysis resistance of the polyester film due to hydrolysis during melt extrusion when drying is insufficient, the dew point in the drying step of the recycled polyester is preferably −60 ° C. or more and −25 ° C. or less. It is more preferably −50 ° C. or higher and −30 ° C. or lower.

Further, if the isocyanate concentration in the air or inert gas in the drying process of the recycled polyester is 0.01 ppm or more, the first carbodiimide compound contained in the recycled material is sufficiently deactivated, and if it is 100 ppm or less, excess It is suppressed that even the 2nd carbodiimide compound newly added at the time of a melt-extrusion process by a simple isocyanate is deactivated. From this viewpoint, the isocyanate concentration in the gas is preferably 0.01 ppm to 70 ppm, and more preferably 0.02 ppm to 50 ppm.

Specifically, a recycled polyester material (chip) containing a carbodiimide compound recovered in the film manufacturing process is put into a drying tower, and contains 0.01 to 100 ppm of isocyanate gas and water vapor (dew point: −25 ° C. or lower). An example is a method in which an inert gas such as air or nitrogen is introduced into a drying tower as hot air, preferably 135 to 180 ° C., more preferably 140 to 175 ° C., and dried for 2 to 8 hours.

The water content of the recycled material dried as described above is preferably less than 100 ppm and more preferably 70 to 20 ppm from the viewpoint of suppressing hydrolysis of the polyester resin. The water content of the recycled material can be measured by, for example, a Karl Fischer moisture meter (manufactured by Kyoto Electronics Industry Co., Ltd., MKC-520).

Intrinsic viscosity (IV)
The intrinsic viscosity (IV) of the recycled polyester material varies depending on the amount of the recycled material. If the recycled material IV is too high, the melt viscosity at the time of melt extrusion increases, the shear heating value increases, and thermal decomposition proceeds. There is a possibility that the AV value increases and the hydrolysis resistance of the film decreases. On the other hand, if the IV of the recycled polyester material is too small, the mechanical properties of the film may be insufficient. From these viewpoints, the intrinsic viscosity (IV) of the recycled polyester material is preferably 0.50 to 1.05 dl / g, and more preferably 0.60 to 0.90 dl / g.
The intrinsic viscosity difference ΔIV between the recycled material and the polyester resin is preferably 0.4 dl / g or less from the viewpoint of ejection stability (thickness unevenness) during extrusion, and is 0.02 to 0.20 dl / More preferably, it is g.

Terminal carboxyl group content (AV)
The terminal carboxyl group amount (AV) of the recycled polyester material varies depending on the blending amount of the recycled material, but if the AV of the recycled material is too large, the hydrolysis resistance of the film may be insufficient. Therefore, the AV of the recycled polyester material is preferably 3 to 20 equivalent / ton, and more preferably 4 to 15 equivalent / ton.
In the present specification, “equivalent / ton” (“eq / ton”, “eq / t”) represents a molar equivalent per ton.

Residual carbodiimide compound content The content of the first carbodiimide compound contained in the recycled polyester material is preferably 0.1 to 2% by mass, more preferably 0.2 to 1.5% by mass, based on the total amount of the recycled polyester material. . Even if the content of the carbodiimide compound contained in the recycled material is 0.1% by mass or more, there is no actual harm when used as a recycled material, and if it is 2% by mass or less, the carbodiimide compound is sufficient with the isocyanate gas at the time of drying. The product quality can be maintained.

The melting point of the recycled polyester material varies depending on the blending amount of the recycled material, but if the melting point of the recycled material is too high, there is a risk that unmelted components are included during melt extrusion and the mechanical strength of the film is lowered. . Therefore, the melting point of the recycled polyester material is preferably in the range of 280 ° C to 320 ° C.

<Melt extrusion process>
50 to 95 parts by mass of a polyester resin, 5 to 50 parts by mass of a recycled polyester material in which the first carbodiimide compound is deactivated by the drying, and a raw material containing the second carbodiimide compound are melted and melted by an extruder. Extrude the resin. The amount of the second carbodiimide compound is such that the total content of the carbodiimide compound contained in the finally produced polyester film is 0.1 to 2% by mass. The “total content of carbodiimide compounds” here refers to all carbodiimide compounds (may include carbodiimide compounds other than the first and second carbodiimide compounds) contained in the produced polyester film. Refers to the total amount.

Polyester resin Physical properties of the polyester resin as a raw material include, for example, a polyester having an intrinsic viscosity (IV) of 0.65 to 0.85 dl / g and a terminal carboxyl group amount (AV) of 15 to 45 equivalents / ton. Resin.

Intrinsic viscosity (IV)
The intrinsic viscosity (IV) of the polyester resin used as a raw material can be adjusted by the polymerization method and polymerization conditions. Specifically, when the solid phase polymerization is performed after the liquid phase polymerization, the intrinsic viscosity (IV) is 0.65 to 0.85 dl / g by adjusting the processing temperature, processing time, processing atmosphere moisture, and oxygen concentration. The polyester resin can be obtained.
In the melt extrusion process of polyester resin, heat is easily generated by shearing, and the amount of terminal carboxyl groups is likely to increase due to thermal decomposition, but if a polyester resin having IV of 0.65 to 0.85 dl / g is used, The raw material resin can be sufficiently kneaded and melted without causing extreme shearing heat generation, and an increase in the amount of terminal carboxyl groups can be effectively suppressed.
The intrinsic viscosity (IV) of the polyester resin used in the present invention is preferably 0.55 to 1.2 dl / g, more preferably 0.6 to 1.1 dl / g.

The intrinsic viscosity (IV) is a specific viscosity (η _sp = η _r −1) obtained by subtracting 1 from the ratio η _r (= η / η ₀ ; relative viscosity) of the solution viscosity (η) and the solvent viscosity (η ₀ ). ) Is divided by the density and extrapolated to a density zero state. IV is obtained from a solution viscosity at 25 ° C. by using a Ubbelohde viscometer, dissolving a polyester resin in a 1,1,2,2-tetrachloroethane / phenol (= 2/3 [mass ratio]) mixed solvent. .

Terminal carboxyl group content (AV)
The terminal carboxyl group amount (AV) of the polyester resin can be adjusted by the polymerization method and polymerization conditions. Specifically, when solid phase polymerization is performed after liquid phase polymerization, the amount of terminal carboxyl groups (AV) is 3 to 55 equivalents / ton by adjusting processing temperature, processing time, processing atmosphere moisture, and oxygen concentration. A polyester resin can be obtained.
When the AV of the polyester raw material resin is 3 equivalents / ton or more, crystallization due to an increase in the linearity of the molecular chain is suppressed, the amount of shear heat generated at the time of melting is not increased, and the AV value of the polyester raw material resin is increased. A decrease in the intrinsic viscosity is suppressed, and when it is 55 equivalents / ton or less, the formed film has sufficient hydrolysis resistance.
The amount of terminal carboxyl groups (AV) of the polyester resin used in the present invention is preferably 3 to 55 equivalents / ton, and more preferably 5 to 50 equivalents / ton.

The terminal carboxyl group amount (AV) was determined by dissolving 0.1 g of a sample in 10 ml of benzyl alcohol, further adding chloroform to obtain a mixed solution, and adding a phenol red indicator dropwise thereto, and adding this solution to a reference solution ( 0.01N KOH-benzyl alcohol mixed solution), and obtained from the amount of the reference solution dropped immediately before the color of the phenol red indicator changes from yellow to red.

Melting point The melting point (Tm) of the polyester resin used in the present invention is preferably in the range of 250 ° C to 300 ° C, more preferably in the range of 255 ° C to 295 ° C. The melting point Tm of the polyester resin is a value determined by a differential scanning calorimetry method.

The polyester resin used as a raw material is preferably dried by contact with hot air of an inert gas (such as nitrogen) at 140 to 170 ° C. or vacuum drying to suppress hydrolysis.

Examples of the polyester resin used as a raw material include a polyester resin obtained by polycondensing a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component.

Esterification Reaction In the esterification reaction when polymerizing polyester, a titanium (Ti) compound is used as a catalyst, and the amount of Ti added is 1 ppm or more and 30 ppm or less, more preferably 2 ppm or more and 20 ppm or less, more preferably, in terms of element. The polymerization is preferably performed in the range of 3 ppm or more and 15 ppm or less. In this case, the polyester film of the present invention contains 1 ppm to 30 ppm of titanium.
When the amount of the Ti-based compound is 1 ppm or more, the polymerization rate is increased and preferable IV is obtained. When the amount of the Ti compound is 30 ppm or less, the amount of terminal carboxyl groups can be adjusted so as to satisfy the above range, and a good color tone can be obtained.

To synthesize a Ti-based polyester using such a Ti compound, for example, Japanese Patent Publication No. 8-30119, Japanese Patent No. 2543624, Japanese Patent No. 3335683, Japanese Patent No. 3717380, Japanese Patent No. 3897756, Japanese Patent No. 396226 Patent No. 397866, Patent No. 3,996,871, Patent No. 40000867, Patent No. 4053837, Patent No. 4127119, Patent No. 4134710, Patent No. 4159154, Patent No. 4269704, Patent No. 4135538, JP-A No. 2005-2005 The methods described in Japanese Patent No. 340616, Japanese Patent Application Laid-Open No. 2005-239940, Japanese Patent Application Laid-Open No. 2004-319444, Japanese Patent Application Laid-Open No. 2007-204538, Japanese Patent No. 3436268, Japanese Patent No. 3780137, and the like can be applied.

Polyesters forming the polyester film of the present invention are (A) malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, Aliphatic dicarboxylic acids such as methylmalonic acid and ethylmalonic acid, alicyclic dicarboxylic acids such as adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, or terephthalic acid, isophthalic acid, phthalic acid, 1 , 4-Naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5 -sodium Selected from the group consisting of dicarboxylic acids such as rufoisophthalic acid, phenylindane dicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, aromatic dicarboxylic acids such as 9,9'-bis (4-carboxyphenyl) fluorenic acid or ester derivatives thereof A dicarboxylic acid component and an aliphatic group such as (B) ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol Diols, cycloaliphatic dimethanol, spiroglycol, isosorbide and other alicyclic diols, or bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'-bis (4-hydroxyphenyl) ) Aromatics such as fluorene A diol component selected from the group consisting of a diol compound of ol, and the like, can be obtained by esterification reaction and / or transesterification in a known method.

It is preferable that at least one aromatic dicarboxylic acid is used as the dicarboxylic acid component. More preferably, the polyester of the present invention contains an aromatic dicarboxylic acid as a main component as a dicarboxylic acid component. The “main component” means that the ratio of the aromatic dicarboxylic acid to the total amount of the dicarboxylic acid component is 80% by mass or more. A dicarboxylic acid component other than the aromatic dicarboxylic acid may be included. Examples of such dicarboxylic acid components other than aromatic dicarboxylic acids include ester derivatives such as aromatic dicarboxylic acids.
Further, it is preferable that at least one aliphatic diol is used as the diol component. The polyester of the present invention can contain ethylene glycol as an aliphatic diol, and preferably contains ethylene glycol as a main component. In addition, a main component means that the ratio of ethylene glycol with respect to diol component whole quantity is 80 mass% or more.

Among these, more preferable polyesters are polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), polycyclohexanedimethylene terephthalate (PCT), or a part of PET. It is copolymerized PET, more preferably PET or copolymerized PET.
The PET is preferably a PET polymerized using one or more selected from a germanium (Ge) compound, an antimony (Sb) compound, an aluminum (Al) compound, and a titanium (Ti) compound, More preferably, a Ti compound is used.

Since the Ti compound has high reaction activity, the polymerization temperature can be lowered. Therefore, in particular, it is possible to suppress the thermal decomposition of PET and the generation of COOH during the polymerization reaction, which is suitable for adjusting the amount of terminal carboxyl groups within a predetermined range in the polyester film of the present invention. .

Examples of the Ti compound include oxides, hydroxides, alkoxides, carboxylates, carbonates, oxalates, organic chelate titanium complexes, and halides. As the Ti-based catalyst, two or more kinds of titanium compounds may be used in combination as long as the effects of the present invention are not impaired.
Examples of Ti-based catalysts include tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate, tetracyclohexyl titanate, tetraphenyl Titanium alkoxide such as titanate and tetrabenzyl titanate, titanium oxide obtained by hydrolysis of titanium alkoxide, titanium-silicon composite oxide or titanium-zirconium composite obtained by hydrolysis of a mixture of titanium alkoxide and silicon alkoxide or zirconium alkoxide Oxide, titanium acetate, titanium oxalate, potassium titanium oxalate, sodium titanium oxalate, potassium titanate, sodium titanate, titanium titanate-aluminum hydroxide mixture, titanium chloride, Titanium - aluminum chloride mixture, titanium acetylacetonate, and organic acids include organic chelate titanium complex having a ligand.

Among the Ti compounds, at least one organic chelate titanium complex having an organic acid as a ligand can be suitably used. Examples of the organic acid include citric acid, lactic acid, trimellitic acid, and malic acid. Among them, an organic chelate complex having citric acid or citrate as a ligand is preferable.

At least one of the polyester resin and the recycled material preferably contains a polyester resin synthesized using a titanium citrate complex as a polymerization catalyst.

For example, when a chelate titanium complex having citric acid as a ligand is used, there is little generation of foreign matters such as fine particles, and a polyester resin having better polymerization activity and color tone than other titanium compounds can be obtained. Furthermore, even when using a citric acid chelate titanium complex, by adding it at the stage of the esterification reaction, a polyester resin having better polymerization activity and color tone and less terminal carboxyl groups can be obtained compared to the case where it is added after the esterification reaction. It is done. In this regard, the titanium catalyst also has a catalytic effect of the esterification reaction. By adding it at the esterification stage, the oligomer acid value at the end of the esterification reaction is lowered, and the subsequent polycondensation reaction is performed more efficiently. In addition, complexes with citric acid as a ligand are more resistant to hydrolysis than titanium alkoxides, etc., and do not hydrolyze in the esterification reaction process, while maintaining the original activity and catalyzing the esterification and polycondensation reactions It is estimated to function effectively as
Also, it is generally known that the greater the amount of terminal carboxyl groups of the polyester resin, the worse the hydrolysis resistance, and the amount of terminal carboxyl groups of the polyester resin is reduced by the addition method of the present invention. Improvement in sex is expected.
As the citrate chelate titanium complex, for example, commercially available products such as VERTEC AC-420 manufactured by Johnson Matthey are easily available.

The aromatic dicarboxylic acid and the aliphatic diol can be introduced by preparing a slurry containing them and continuously supplying it to the esterification reaction step.

The polyester resin according to the present invention polymerizes an aromatic dicarboxylic acid and an aliphatic diol in the presence of a catalyst containing a titanium compound, and at least one of the titanium compounds is an organic chelate titanium having an organic acid as a ligand. An esterification reaction step including at least a process of adding an organic chelate titanium complex, a magnesium compound and a pentavalent phosphate ester having no aromatic ring as a substituent in this order, and an esterification reaction step And a polycondensation step in which a polycondensation product is produced by subjecting the esterification reaction product thus obtained to a polycondensation reaction.

In this case, in the course of the esterification reaction, the addition of a magnesium compound to the presence of an organic chelate titanium complex as a titanium compound, followed by the addition order of adding a specific pentavalent phosphorus compound, thereby providing a titanium catalyst. It is possible to effectively suppress the decomposition reaction in the polycondensation while keeping the reaction activity of the compound moderately high, imparting electrostatic application characteristics with magnesium. Therefore, as a result, a polyester resin having little coloring, high electrostatic application characteristics, and improved yellowing when exposed to high temperatures is obtained.
As a result, coloring during polymerization and subsequent coloring during melt film formation are reduced, and yellowishness is reduced compared to conventional antimony (Sb) catalyst-based polyester resins, and germanium catalysts having a relatively high transparency are also obtained. It is possible to provide a polyester resin having a color tone and transparency comparable to a polyester resin and having excellent heat resistance. In addition, a polyester resin having high transparency and less yellowness can be obtained without using a color tone adjusting material such as a cobalt compound or a pigment.

Phosphorus compound As the pentavalent phosphorus compound, at least one pentavalent phosphate having no aromatic ring as a substituent can be used. Examples of the pentavalent phosphate ester in the present invention include trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, tris phosphate (triethylene glycol), methyl acid phosphate, and phosphoric acid. Examples include ethyl acid, isopropyl acid phosphate, butyl acid phosphate, monobutyl phosphate, dibutyl phosphate, dioctyl phosphate, and triethylene glycol acid phosphate.

Among these pentavalent phosphates, phosphates having a lower alkyl group having 2 or less carbon atoms as a substituent [(OR) ₃ —P═O; R is an alkyl group having 1 or 2 carbon atoms. Are preferred. Specifically, trimethyl phosphate and triethyl phosphate are particularly preferred.

In particular, when the chelate titanium complex coordinated with citric acid or a salt thereof is used as the catalyst as the titanium compound, the pentavalent phosphate ester has better polymerization activity and color tone than the trivalent phosphate ester. . Furthermore, in the case of adding a pentavalent phosphate having 2 or less carbon atoms, the balance of polymerization activity, color tone, and heat resistance can be particularly improved.

The amount of phosphorus compound added is preferably such that the P element conversion value is in the range of 50 ppm to 90 ppm. The amount of the phosphorus compound is more preferably 60 ppm to 80 ppm, and still more preferably 65 ppm to 75 ppm.

Magnesium compound Inclusion of a magnesium compound in the course of the esterification reaction improves electrostatic applicability. In general, when a magnesium compound is used, coloring tends to occur. However, in the present invention, the coloring is suppressed, and a polyester resin having excellent color tone and heat resistance can be obtained.

Examples of the magnesium compound include magnesium salts such as magnesium oxide, magnesium hydroxide, magnesium alkoxide, magnesium acetate, and magnesium carbonate. Among these, magnesium acetate is preferable from the viewpoint of solubility in ethylene glycol.

As the addition amount of the magnesium compound, in order to impart high electrostatic applicability, the Mg element conversion value is preferably 50 ppm or more, and more preferably 50 ppm or more and 100 ppm or less. The addition amount of the magnesium compound is preferably such that the Mg element conversion value is in the range of 60 ppm or more and 90 ppm or less, and more preferably in the range of 70 ppm or more and 80 ppm or less in terms of imparting electrostatic applicability. .

The esterification reaction may be carried out using a multistage apparatus in which at least two reactors are connected in series under conditions where ethylene glycol is refluxed while removing water or alcohol produced by the reaction from the system. it can.

The esterification reaction described above may be performed in one stage or may be performed in multiple stages.
When the esterification reaction is carried out in one stage, the esterification reaction temperature is preferably 230 to 260 ° C, more preferably 240 to 250 ° C.
When the esterification reaction is carried out in multiple stages, the temperature of the esterification reaction in the first reaction tank is preferably 230 to 260 ° C, more preferably 240 to 250 ° C, and the pressure is 1.0 to 5.0 kg / cm ² is preferable, and 2.0 to 3.0 kg / cm ² is more preferable. The temperature of the esterification reaction in the second reaction tank is preferably 230 to 260 ° C., more preferably 245 to 255 ° C., and the pressure is 0.5 to 5.0 kg / cm ² , more preferably 1.0 to 3. 0 kg / cm ² . Furthermore, when carrying out by dividing into three or more stages, it is preferable to set the conditions of the esterification reaction in the intermediate stage to a condition between the conditions of the first reaction tank and the final reaction tank.

Polycondensation In the polycondensation step, a polycondensation product is produced by subjecting the esterification reaction product produced in the esterification reaction to a polycondensation reaction. The polycondensation reaction may be performed in one stage or may be performed in multiple stages.

The esterification reaction product such as an oligomer generated by the esterification reaction is subsequently subjected to a polycondensation reaction. This polycondensation reaction can be suitably performed by supplying an esterification reaction product to a multistage polycondensation reaction tank.

For example, the polycondensation reaction conditions in a three-stage reaction tank are as follows: the first reaction tank has a reaction temperature of 255 to 280 ° C., more preferably 265 to 275 ° C., and a pressure of 100 to 10 torr (13.3). × 10 ⁻³ to 1.3 × 10 ⁻³ MPa), more preferably 50 to 20 torr (6.67 × 10 ⁻³ to 2.67 × 10 ⁻³ MPa). The temperature is 265 to 285 ° C., more preferably 270 to 280 ° C., and the pressure is 20 to 1 torr (2.67 × 10 ⁻³ to 1.33 × 10 ⁻⁴ MPa), more preferably 10 to 3 torr (1. 33 × 10 ⁻³ to 4.0 × 10 ⁻⁴ MPa), and the third reaction tank which is the final reaction tank has a reaction temperature of 270 to 290 ° C., more preferably 275 to 285 ° C., and a pressure of 10 to 0.1 torr ( ^{^{.33 × 10 -3 ~ 1.33 × 10}} -5 MPa), aspect is preferably more preferably ^{5 ~ 0.5torr (6.67 × 10 -4} ~ 6.67 × 10 -5 MPa).

The polyester resin used in the present invention is preferably polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), polycyclohexanedimethylene terephthalate (PCT), or copolymerized PET obtained by modifying a part of PET. More preferred is PET or copolymerized PET.
Such a polyester film has a constitutional component in which the total of carboxylic acid groups and hydroxyl groups is 3 or more (hereinafter sometimes referred to as “≧ trifunctional component”), or an isocyanate compound, a carbodiimide compound, and an epoxy compound. It is preferable that at least one kind of end capping agent selected from the group consisting of: These “≧ 3 functional components” and “terminal blocking agent” may be used alone or in combination.

It is preferable that the polyester film of the present invention contains “≧ 3 functional component”, that is, a constituent component in which the total number (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) is 3 or more. Here, the carboxylic acid composition in which the total number (a + b) of the carboxylic acid group number (a) and the hydroxyl group number (b) is 3 or more (≧ trifunctional component: p) and the carboxylic acid group number (a) is 3 or more. Examples of ingredients include trifunctional aromatic carboxylic acid constituents such as trimesic acid, trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, and anthracentricarboxylic acid, methanetricarboxylic acid, ethanetricarboxylic acid, propanetricarboxylic acid, and Trifunctional aliphatic carboxylic acid constituents such as butanetricarboxylic acid, tetrafunctional aromatic carboxylic acids such as benzenetetracarboxylic acid, benzophenonetetracarboxylic acid, naphthalenetetracarboxylic acid, anthracenetetracarboxylic acid, and berylenetetracarboxylic acid Constituents, ethanetetracarboxylic acid, ethylene Tetrafunctional aliphatic carboxylic acid constituents such as lacarboxylic acid, butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, cyclohexanetetracarboxylic acid, and adamantanetetracarboxylic acid, benzenepentacarboxylic acid, benzenehexacarboxylic acid, naphthalenepentacarboxylic acid Pentafunctional or higher aromatic carboxylic acid components such as naphthalene hexacarboxylic acid, naphthalene heptacarboxylic acid, naphthalene octacarboxylic acid, anthracene pentacarboxylic acid, anthracene hexacarboxylic acid, anthracene heptacarboxylic acid, and anthracene octacarboxylic acid, ethane Pentacarboxylic acid, ethaneheptacarboxylic acid, butanepentacarboxylic acid, butaneheptacarboxylic acid, cyclopentanepentacarboxylic acid, cyclohexanepentacarboxylic acid, Cyclohexane hexacarboxylic acid, adamantane penta carboxylic acid, and penta-functional or more aliphatic carboxylic acid component such as adamantane hexacarboxylic acid, as well as ester derivatives thereof and acid anhydrides thereof, but are not limited to. In addition, it is also preferable to add oxyacids such as l-lactide, d-lactide, hydroxybenzoic acid and the like, or a combination of a plurality of such oxyacids to the carboxy terminal of the carboxylic acid component. Used. Moreover, these may be used independently or may be used in multiple types as needed.

Examples of the component having 3 or more hydroxyl groups (b) include trifunctional aromatic components such as trihydroxybenzene, trihydroxynaphthalene, trihydroxyanthracene, trihydroxychalcone, trihydroxyflavone, and trihydroxycoumarin. Examples of the component and trifunctional aliphatic alcohol component include trifunctional aliphatic alcohol components such as glycerin, trimethylolpropane, and propanetriol, and tetrafunctional aliphatic alcohol components such as pentaerythritol. Moreover, the structural component which added diol to the hydroxyl-terminal of the above-mentioned compound is also preferably used. Moreover, these may be used independently or may be used in multiple types as needed.

Other examples of the constituent component (≧ trifunctional component: p) include both hydroxy and carboxylic acid groups in one molecule such as hydroxyisophthalic acid, hydroxyterephthalic acid, dihydroxyterephthalic acid, and dihydroxyterephthalic acid. Among the oxyacids possessed, those having a total (a + b) of the number of carboxylic acid groups (a) and the number of hydroxyl groups (b) of 3 or more can be mentioned. In addition, oxyacids such as l-lactide, d-lactide, and hydroxybenzoic acid, and derivatives thereof, or a combination of a plurality of such oxyacids added to the carboxy terminus of the above-described constituents are also preferably used. . Moreover, these may be used independently or may be used in multiple types as needed.

In the polyester film of the present invention, the content of the constituent component (≧ trifunctional component: p) is 0.005 mol% to 2.5 mol% with respect to the amount of all the constituent components in the polyester film. preferable. More preferably, it is 0.020 mol% or more and 1 mol% or less, More preferably, it is 0.025 mol% or more and 1 mol% or less, More preferably, it is 0.035 mol% or more and 0.5 mol% or less, More preferably, it is 0.05. The mol% is 0.5 mol% or less, particularly preferably 0.1 mol% or more and 0.25 mol% or less.
When a coating layer is provided as an adjacent layer, a functional group that has not been used for polycondensation has a hydrogen bond and / or a covalent bond with a component in the coating layer due to the presence of ≧ 3 functional components in the polyester film. The adhesion with the coating layer can be further improved.

At least one of the polyester resin and the recycled polyester material is a 1,4-cyclohexanedimethanol (CHDM) -containing polyester (CHDM polyester such as polycyclohexanedimethylene terephthalate (CHDM)). PCT)).

(1) CHDM-type polyester The CHDM-type polyester preferably contains a structure derived from 1,4-cyclohexanedimethanol in an amount of 0.1 to 20 mol% or 80 to 100 mol% based on the total amount of the structure derived from the diol component. More preferably 0.5 mol% to 16 mol% or 83 mol% to 98 mol%, and particularly preferably 1 mol% to 12 mol% or 86 mol% to 96 mol%.
As described above, the two regions of the CHDM-derived structure are low (0.1 to 20 mol%) and high (80 to 100 mol%). The polyester easily takes a crystal structure in these regions. This is because high mechanical strength and heat resistance are easily exhibited.
By using these CHDM polyesters, it is possible to produce a polyester film that is excellent in hydrolysis resistance and further has mechanical strength and heat resistance.

Examples of the diol component of the material for forming units other than the structure derived from 1,4-cyclohexanedimethanol of the CHDM polyester include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4 Aliphatic diols such as butanediol, 1,2-butanediol and 1,3-butanediol, alicyclic diols such as spiroglycol and isosorbide, and bisphenol A, 1,3-benzenedimethanol, Representative examples include diols such as aromatic diols such as 1,4-benzenedimethanol and 9,9′-bis (4-hydroxyphenyl) fluorene, but are not limited thereto. Among these, it is preferable to use ethylene glycol.

Examples of the dicarboxylic acid component of the material for forming units other than the structure derived from 1,4-cyclohexanedimethanol of the CHDM polyester include terephthalic acid, isophthalic acid, malonic acid, succinic acid, glutaric acid, adipic acid , Suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalonic acid, ethylmalonic acid and other aliphatic dicarboxylic acids, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, Cycloaliphatic dicarboxylic acid, alicyclic dicarboxylic acid such as decalin dicarboxylic acid, and isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8 -Naphthalene range Rubonic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenylether dicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylindanedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid, and 9,9′-bis (4 -Carboxyphenyl) A dicarboxylic acid such as an aromatic dicarboxylic acid such as fluoric acid, or an ester derivative thereof is given as a representative example, but is not limited thereto.
The CHDM polyester preferably includes at least a structure derived from terephthalic acid as a dicarboxylic component.
In the present invention, isophthalic acid (IPA) may be added in addition to terephthalic acid as the dicarboxylic acid component of the CHDM polyester. The amount of IPA is preferably 0 mol% or more and 15 mol% or less, more preferably 0 mol% or more and 12 mol% or less, still more preferably 0 mol% or more and 9 mol% or less with respect to the total amount of the dicarboxylic acid component.

Since CHDM polyester such as polycyclohexanedimethylene terephthalate (PCT) tends to have a high intrinsic viscosity (IV), the IV of CHDM polyester is preferably 1.2 dl / g or less, more preferably 1. It is 15 dl / g or less, More preferably, it is 1.1 dl / g or less.

Further, since the melting point of CHDM polyester such as polycyclohexanedimethylene terephthalate (PCT) is about 275 ° C. and about 20 ° C. higher than PET, the extrusion temperature of CHDM polyester is preferably 320 ° C. or less, more preferably 315 ° C or lower, more preferably 310 ° C or lower.

Carbodiimide compound The recycled material of the present invention includes a carbodiimide compound having a carbodiimide group (first carbodiimide compound). Furthermore, a carbodiimide compound having a carbodiimide group (second carbodiimide compound) is used as a terminal blocking agent in a part of the raw material for the melt extrusion process (hereinafter, the first carbodiimide compound and the second carbodiimide compound are used). Collectively, they are sometimes simply referred to as “carbodiimide compounds”.) In the present invention, the first carbodiimide compound and the second carbodiimide compound may be the same as or different from each other.
In addition to the carbodiimide compound, for example, an oxazoline compound and an epoxy compound can be used as the end-capping agent for the polyester resin. The carbodiimide compound exhibits a sealing effect in a relatively small amount, and an unreacted component is included. Even after film formation, a high sealing reaction (so-called ambush effect) is achieved.

Examples of carbodiimide compounds include monofunctional carbodiimides and polyfunctional carbodiimides.
Examples of monofunctional carbodiimides include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, t-butylisopropylcarbodiimide, diphenylcarbodiimide, di-t-butylcarbodiimide and di-β-naphthylcarbodiimide. Particularly preferred are dicyclohexylcarbodiimide and diisopropylcarbodiimide.

As the polyfunctional carbodiimide, polycarbodiimide having a polymerization degree of 3 to 15 is preferably used. The polycarbodiimide generally has a repeating unit represented by “—R—N═C═N—” or the like, and the R represents a divalent linking group such as alkylene or arylene. Examples of such repeating units include 1,5-naphthalene carbodiimide, 4,4′-diphenylmethane carbodiimide, 4,4′-diphenyldimethylmethane carbodiimide, 1,3-phenylene carbodiimide, 2,4-tolylene carbodiimide, 2,6-tolylenecarbodiimide, mixture of 2,4-tolylenecarbodiimide and 2,6-tolylenecarbodiimide, hexamethylenecarbodiimide, cyclohexane-1,4-carbodiimide, xylylenecarbodiimide, isophoronecarbodiimide, dicyclohexylmethane-4, 4'-carbodiimide, methylcyclohexanecarbodiimide, tetramethylxylylene carbodiimide, 2,6-diisopropylphenylcarbodiimide and 1,3,5-triisopropylbenzene Such as 2,4-carbodiimide can be exemplified.

The carbodiimide compound used as the end-capping agent is preferably a carbodiimide compound having high heat resistance in that generation of isocyanate gas due to thermal decomposition is suppressed. In order to improve heat resistance, a carbodiimide compound having a higher molecular weight (degree of polymerization) is more preferable, and it is more preferable that the terminal of the carbodiimide compound has a structure having high heat resistance. Further, by lowering the temperature at which the polyester resin is melt-extruded, the effect of improving weather resistance and the effect of reducing thermal shrinkage by the carbodiimide compound can be obtained more effectively.

Examples of commercially available carbodiimide end-capping agents include STABAXOL P (molecular weight: 3000 to 4000), STABAXOL P200 (molecular weight: about 2000), and STABAXOL P400 (molecular weight: about 20000) (above, Rhein Chemie). Japan Co., Ltd.), LA-1 (molecular weight: about 2000, manufactured by Nisshinbo Chemical Co., Ltd.), STABILIZER 9000 (molecular weight: about 20000, manufactured by Rhein Chemie), etc., but are not limited thereto. .

At least one of the first carbodiimide compound contained in the recycled polyester material and the second carbodiimide compound contained in the raw material has one carbodiimide group, and the first nitrogen and the second nitrogen are bonded by a bonding group. It may be a cyclic carbodiimide compound containing a cyclic structure.

The carbodiimide compound containing a cyclic structure preferably has a molecular weight of 400 or more, more preferably 500 to 1500.

The compound having a cyclic structure in which one carbodiimide group is included and the first nitrogen and the second nitrogen are bonded to each other through a bonding group may have a plurality of cyclic structures.

The cyclic structure has one carbodiimide group (—N═C═N—), and the first nitrogen and the second nitrogen are bonded by a bonding group. One cyclic structure has only one carbodiimide group. For example, when there are a plurality of cyclic structures in the molecule, such as a spiro ring, one cyclic structure bonded to a spiro atom is included in each cyclic structure. Needless to say, the compound may have a plurality of carbodiimide groups as long as it has a carbodiimide group. The number of atoms in the cyclic structure is preferably 8 to 50, more preferably 10 to 30, further preferably 10 to 20, and particularly preferably 10 to 15.

Here, the number of atoms in the cyclic structure means the number of atoms directly constituting the cyclic structure, and is, for example, 8 for an 8-membered ring and 50 for a 50-membered ring. When the number of atoms in the cyclic structure is smaller than 8, the stability of the cyclic carbodiimide compound is lowered, and it may be difficult to store and use. From the viewpoint of reactivity, there is no particular limitation on the upper limit of the number of ring members, but cyclic carbodiimide compounds having more than 50 atoms are difficult to synthesize, and the cost may increase significantly. From this viewpoint, the number of atoms in the cyclic structure is preferably selected from the range of 10 to 30, more preferably 10 to 20, and particularly preferably 10 to 15.

The ring structure is preferably a structure represented by the following formula (1).

In the formula (1), Q represents a divalent to tetravalent linking group that is an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof, each of which may contain a heteroatom and a substituent. A heteroatom in this case refers to O, N, S, or P. Two of the valences of this linking group are used to form a cyclic structure. When Q is a trivalent or tetravalent linking group, it is bonded to a polymer or other cyclic structure via a single bond, a double bond, an atom, or an atomic group.

That is, the linking group (Q) is a divalent to tetravalent aliphatic group having 1 to 20 carbon atoms and a divalent to tetravalent carbon atom having 3 to 20 carbon atoms, which may each contain a heteroatom and a substituent. A linking group is selected which is a cyclic group, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof, and has the necessary number of carbon atoms to form the cyclic structure defined above. Examples of the combination include structures such as an alkylene-arylene group in which an alkylene group and an arylene group are bonded.
The linking group (Q) is preferably a divalent to tetravalent linking group represented by the following formula (1-1), (1-2) or (1-3).

In formula (1-1), Ar ¹ and Ar ² each independently represent a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, which may contain a hetero atom and a substituent, respectively.
Examples of the aromatic group represented by Ar ¹ or Ar ² include an arylene group having 5 to 15 carbon atoms and an arene having 5 to 15 carbon atoms, each of which contains a hetero atom and may have a heterocyclic structure. Examples include triyl group and arenetetrayl group having 5 to 15 carbon atoms. Examples of the arylene group (divalent) include a phenylene group and a naphthalenediyl group. Examples of the arenetriyl group (trivalent) include a benzenetriyl group and a naphthalenetriyl group. Examples of the arenetetrayl group (tetravalent) include a benzenetetrayl group and a naphthalenetetrayl group. These aromatic groups may be substituted. Examples of the substituent include alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 15 carbon atoms, halogen atoms, nitro groups, amide groups, hydroxyl groups, ester groups, ether groups, and aldehyde groups. .

In formula (1-2), R ¹ and R ² each independently contain a heteroatom and a substituent, each of which is a divalent to tetravalent C 1-20 aliphatic group or divalent to tetravalent. Represents an alicyclic group having 3 to 20 carbon atoms, a combination thereof, or a combination of these aliphatic group or alicyclic group and a divalent to tetravalent aromatic group having 5 to 15 carbon atoms.

Examples of the aliphatic group include an alkylene group having 1 to 20 carbon atoms, an alkanetriyl group having 1 to 20 carbon atoms, and an alkanetetrayl group having 1 to 20 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a dodecylene group, and a hexadecylene group. Examples of alkanetriyl groups include methanetriyl group, ethanetriyl group, propanetriyl group, butanetriyl group, pentanetriyl group, hexanetriyl group, heptanetriyl group, octanetriyl group, nonanthriyl group, decantriyl group, dodecantriyl group. Yl group and hexadecantriyl group. Examples of alkanetetrayl groups include methanetetrayl, ethanetetrayl, propanetetrayl, butanetetrayl, pentanetetrayl, hexanetetrayl, heptanetetrayl, octanetetrayl, nonane Examples include a tetrayl group, a decanetetrayl group, a dodecanetetrayl group, and a hexadecanetetrayl group. These aliphatic groups may be substituted. Examples of the substituent include alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 15 carbon atoms, halogen atoms, nitro groups, amide groups, hydroxyl groups, ester groups, ether groups, and aldehyde groups. .

Examples of the alicyclic group include a cycloalkylene group having 3 to 20 carbon atoms, a cycloalkanetriyl group having 3 to 20 carbon atoms, and a cycloalkanetetrayl group having 3 to 20 carbon atoms. Examples of the cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a cyclooctylene group, a cyclononylene group, a cyclodecylene group, a cyclododecylene group, and a cyclohexadecylene group. Can be mentioned. Examples of alkanetriyl groups include cyclopropanetriyl, cyclobutanetriyl, cyclopentanetriyl, cyclohexanetriyl, cycloheptanetriyl, cyclooctanetriyl, cyclononanetriyl, cyclode A cantriyl group, a cyclododecantriyl group, and a cyclohexadecanetriyl group are mentioned. Examples of alkanetetrayl groups include cyclopropanetetrayl, cyclobutanetetrayl, cyclopentanetetrayl, cyclohexanetetrayl, cycloheptanetetrayl, cyclooctanetetrayl, cyclononanetetrayl, cyclo A decane tetrayl group, a cyclododecane tetrayl group, and a cyclohexadecane tetrayl group are mentioned. These alicyclic groups may be substituted. Examples of the substituent include alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 15 carbon atoms, halogen atoms, nitro groups, amide groups, hydroxyl groups, ester groups, ether groups, and aldehyde groups. .

Examples of the aromatic group include an arylene group having 5 to 15 carbon atoms, an arylene triyl group having 5 to 15 carbon atoms, and a carbon number of 5 each optionally containing a hetero atom and having a heterocyclic structure. ˜15 arenetetrayl groups. Examples of the arylene group include a phenylene group and a naphthalenediyl group. Examples of the arenetriyl group (trivalent) include a benzenetriyl group and a naphthalenetriyl group. Examples of the arenetetrayl group (tetravalent) include a benzenetetrayl group and a naphthalenetetrayl group. These aromatic groups may be substituted. Examples of the substituent include alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 15 carbon atoms, halogen atoms, nitro groups, amide groups, hydroxyl groups, ester groups, ether groups, and aldehyde groups. .

In the above formulas (1-1) and (1-2), X ¹ and X ² are each independently a divalent to tetravalent C 1-20 aliphatic optionally containing a heteroatom and a substituent. Group, a divalent to tetravalent alicyclic group having 3 to 20 carbon atoms, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof.

In the above formulas (1-1) and (1-2), s and k each independently represent an integer of 0 to 10, preferably an integer of 0 to 3, more preferably an integer of 0 to 1.
This is because if s or k exceeds 10, synthesis of the cyclic carbodiimide compound becomes difficult, and the cost may increase significantly. From this viewpoint, the integer represented by s or k is preferably selected in the range of 0 to 3. When s or k is 2 or more, X ¹ or X ² as a plurality of repeating units may be different from each other.

In the above formula (1-3), X ³ each may contain a heteroatom and a substituent, a divalent to tetravalent C 1-20 aliphatic group, a divalent to tetravalent carbon number of 3 to 20 Represents an alicyclic group, a divalent to tetravalent aromatic group having 5 to 15 carbon atoms, or a combination thereof.

Examples of the aliphatic group include an alkylene group having 1 to 20 carbon atoms, an alkanetriyl group having 1 to 20 carbon atoms, and an alkanetetrayl group having 1 to 20 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a dodecylene group, and a hexadecylene group. Examples of alkanetriyl groups include methanetriyl group, ethanetriyl group, propanetriyl group, butanetriyl group, pentanetriyl group, hexanetriyl group, heptanetriyl group, octanetriyl group, nonanthriyl group, decantriyl group, dodecantriyl group. Yl group and hexadecantriyl group. Examples of alkanetetrayl groups include methanetetrayl, ethanetetrayl, propanetetrayl, butanetetrayl, pentanetetrayl, hexanetetrayl, heptanetetrayl, octanetetrayl, nonane Examples include a tetrayl group, a decanetetrayl group, a dodecanetetrayl group, and a hexadecanetetrayl group.
These aliphatic groups may contain a substituent. Examples of the substituent include alkyl groups having 1 to 20 carbon atoms, aryl groups having 6 to 15 carbon atoms, halogen atoms, nitro groups, amide groups, hydroxyl groups. Groups, ester groups, ether groups, and aldehyde groups.

Examples of the alicyclic group include a cycloalkylene group having 3 to 20 carbon atoms, a cycloalkanetriyl group having 3 to 20 carbon atoms, and a cycloalkanetetrayl group having 3 to 20 carbon atoms. Examples of the cycloalkylene group include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a cyclooctylene group, a cyclononylene group, a cyclodecylene group, a cyclododecylene group, and a cyclohexadecylene group. Can be mentioned. Examples of alkanetriyl groups include cyclopropanetriyl, cyclobutanetriyl, cyclopentanetriyl, cyclohexanetriyl, cycloheptanetriyl, cyclooctanetriyl, cyclononanetriyl, cyclode A cantriyl group, a cyclododecantriyl group, and a cyclohexadecanetriyl group are mentioned. Examples of alkanetetrayl groups include cyclopropanetetrayl, cyclobutanetetrayl, cyclopentanetetrayl, cyclohexanetetrayl, cycloheptanetetrayl, cyclooctanetetrayl, cyclononanetetrayl, cyclo A decane tetrayl group, a cyclododecane tetrayl group, and a cyclohexadecane tetrayl group are mentioned. These alicyclic groups may contain a substituent. Examples of the substituent include an alkyl group having 1 to 20 carbon atoms, an arylene group having 6 to 15 carbon atoms, a halogen atom, a nitro group, an amide group, Examples include hydroxyl groups, ester groups, ether groups, and aldehyde groups.

Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ may each contain a hetero atom. When Q is a divalent linking group, Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ all represent a divalent group. When Q is a trivalent linking group, one of Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ represents a trivalent group. When Q is a tetravalent linking group, one of Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² and X ³ represents a tetravalent group, or two are trivalent Represents a group.

Examples of the cyclic carbodiimide compound that can be used in the present invention include compounds represented by the following (a) to (c).

Cyclic carbodiimide compound (a)
Examples of the cyclic carbodiimide compound used in the present invention include a compound represented by the following formula (2) (hereinafter sometimes referred to as “cyclic carbodiimide compound (a)”).

Wherein (2), Q _a is an aliphatic group, an alicyclic group, an aromatic group or a divalent linking group which is a combination of these, it may contain a heteroatom. The definitions of the aliphatic group, alicyclic group, and aromatic group are the same as the definitions of the aliphatic group, alicyclic group, and aromatic group in Q described in Formula (1). However, in the compound of formula (2), the aliphatic group represented by Q _a, alicyclic group, aromatic group are all divalent group. Q _a is preferably a divalent linking group represented by the following formula (2-1), (2-2) or (2-3).

In formulas (2-1) to (2-3), the definitions of Ar _a ¹ , Ar _a ² , R _a ¹ , R _a ² , X _a ¹ , X _a ² , X _a ³ , s and k are respectively The same as the definitions of Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² , X ³ , s and k in the formulas (1-1) to (1-3). However, these all represent a divalent group.
Examples of the cyclic carbodiimide compound (a) include the following compounds.

Cyclic carbodiimide compound (b)
Furthermore, examples of the cyclic carbodiimide compound used in the present invention include a compound represented by the following formula (3) (hereinafter sometimes referred to as “cyclic carbodiimide compound (b)”).

Wherein (3), Q _b is an aliphatic group, an alicyclic group, an aromatic group or a trivalent linking group combinations thereof, and may contain a hetero atom. Y represents a carrier supporting a cyclic structure. The definitions of the aliphatic group, alicyclic group, and aromatic group are the same as the definitions of the aliphatic group, alicyclic group, and aromatic group in Q described in Formula (1). However, in the compound of formula (3), the inner one of the group constituting the Q _b is a trivalent group.
Q _b is preferably a trivalent linking group represented by the following formula (3-1), (3-2) or (3-3).

In the formulas (3-1) to (3-3), Ar _b ¹ , Ar _b ² , R _b ¹ , R _b ² , X _b ¹ , X _b ² , X _b ³ , s and k are defined as follows: Each has the same definition as Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² , X ³ , s and k in formulas (1-1) to (1-3). However, one of these represents a trivalent group.
Y is preferably a single bond, a double bond, an atom, an atomic group or a polymer. Y is a bonding portion, and a plurality of cyclic structures are bonded via Y to form a structure represented by the formula (3).
Examples of the cyclic carbodiimide compound (b) include the following compounds.

Cyclic carbodiimide compound (c)
Furthermore, examples of the cyclic carbodiimide compound used in the present invention include a compound represented by the following formula (4) (hereinafter sometimes referred to as “cyclic carbodiimide compound (c)”).

In formula (4), Q _c is any one tetravalent linking group selected from the group consisting of an aliphatic group, an alicyclic group, and an aromatic group, or an aliphatic group, an alicyclic group, And a tetravalent linking group that is a combination of two or more groups selected from the group consisting of aromatic groups, and may further have a heteroatom. Z ¹ and Z ² each independently represent a carrier carrying a cyclic structure. Z ¹ and Z ² may be bonded to each other to form a cyclic structure.
The definitions of the aliphatic group, the alicyclic group, and the aromatic group are the same as the definitions of the aliphatic group, the alicyclic group, and the aromatic group in Q described in Formula (1). However, in the compound of the formula (4), Q _c is a tetravalent group. Accordingly, one of these groups is a tetravalent group or two are trivalent groups.
Q _c is preferably a tetravalent linking group represented by the following formula (4-1), formula (4-2), or formula (4-3).

In the formulas (4-1) to (4-3), Ar _c ¹ , Ar _c ² , R _c ¹ , R _c ² , X _c ¹ , X _c ² , X _c ³ , s and k are defined as follows: These are the same as the definitions of Ar ¹ , Ar ² , R ¹ , R ² , X ¹ , X ² , X ³ , s and k in the formulas (1-1) to (1-3), respectively. Provided that Ar _c ¹ , Ar _c ² , R _c ¹ , R _c ² , X _c ¹ , X _c ² and X _c ³ are one of these being a tetravalent group or two of which are trivalent It is a group. Z ¹ and Z ² are preferably each independently a single bond, a double bond, an atom, an atomic group or a polymer. Z ¹ and Z ² are bonding portions, and a plurality of cyclic structures are bonded via Z ¹ and Z ² to form a structure represented by the formula (4).
Examples of the cyclic carbodiimide compound (c) include the following compounds.

Method for Producing Cyclic Carbodiimide Compound The cyclic carbodiimide compound according to the present invention can be synthesized based on the method described in paragraph [0076] of JP-A No. 2011-256337.

The blending amount of the second carbodiimide compound added as the end-capping agent is such that the total content of the carbodiimide compound is 100 parts by mass in total of the polyester resin and the recycled polyester material containing the first carbodiimide compound after drying. What is necessary is just to set according to the kind and quantity of a polyester resin and a recycled material, film forming conditions, etc. so that the polyester film which is 0.1-2.0 mass parts may be obtained.

When used as a masterbatch containing a polyester resin and a carbodiimide compound, for example, it is preferable to perform a drying treatment by contacting hot air of an inert gas (such as nitrogen) at 135 to 170 ° C., for example. Alternatively, vacuum drying may be performed. If the carbodiimide compound is in powder form, it may be used as it is without being dried.

Other additives As raw materials used for melt extrusion, in addition to the above-mentioned polyester resin, recycled polyester material, carbodiimide compound, additives such as end-capping agents, light stabilizers, or antioxidants other than carbodiimide compounds are used. It can further contain in the range which does not impair the effect of invention.

It is preferable that a light stabilizer is added to the polyester film produced according to the present invention. By containing the light stabilizer, it is possible to prevent ultraviolet degradation. Examples of light stabilizers include compounds that absorb light such as ultraviolet rays and convert them into thermal energy, and materials that absorb radicals generated by light absorption and decomposition and suppress decomposition chain reactions. Can be mentioned.

The light stabilizer is preferably a compound that absorbs light such as ultraviolet rays and converts it into heat energy. By including such a light stabilizer in the film, it becomes possible to keep the effect of improving the partial discharge voltage by the film high for a long time even if the film is irradiated with ultraviolet rays continuously for a long time. Changes in color tone, strength deterioration, and the like due to UV rays.

For example, as an ultraviolet absorber, as long as other properties of the polyester are not impaired, any of an organic ultraviolet absorber, an inorganic ultraviolet absorber, and a combination thereof are preferably used without any particular limitation. be able to. On the other hand, it is desired that the ultraviolet absorber is excellent in moisture and heat resistance and can be uniformly dispersed in the film.

Examples of the ultraviolet absorber include organic ultraviolet absorbers such as salicylic acid-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ultraviolet absorbers, and hindered amine-based ultraviolet stabilizers. Specifically, for example, salicylic acid ultraviolet absorbers such as pt-butylphenyl salicylate and p-octylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4- Benzophenone ultraviolet absorbers such as methoxy-5-sulfobenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, and bis (2-methoxy-4-hydroxy-5-benzoylphenyl) methane, 2- (2 '-Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-5'-methylphenyl) benzotriazole, and 2,2'-methylenebis [4- (1,1,3,3-tetra Methylbutyl) -6- (2Hbenzotriazol-2-yl) phenol Benzotriazole ultraviolet absorbers such as ethyl-2-cyano-3,3′-diphenyl acrylate), 2- (4,6-diphenyl-1,3,5-triazine- 2-yl) -5-[(hexyl) oxy] -phenol and other triazine UV absorbers, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, dimethyl succinate 1- (2 -Hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate and other hindered amine ultraviolet absorbers, nickel bis (octylphenyl) sulfide, and 2,4-di-t-butyl And phenyl-3 ′, 5′-di-t-butyl-4′-hydroxybenzoate.
Of these ultraviolet absorbers, triazine-based ultraviolet absorbers are preferable in that they have high resistance to repeated ultraviolet absorption. In addition, these ultraviolet absorbers may be added to the film by the above-mentioned ultraviolet absorber alone, or in a form in which a monomer having ultraviolet absorbing ability is copolymerized with an organic conductive material or a water-insoluble resin. It may be introduced.

The content of the light stabilizer in the polyester film is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.3% by mass or more and 7% by mass or less with respect to the total mass of the polyester film. More preferably, it is 0.7 mass% or more and 4 mass% or less. By setting the content of the light stabilizer in the above range, it is possible to suppress a decrease in the molecular weight of the polyester due to light degradation over a long period of time, and it is possible to suppress a decrease in adhesion due to cohesive failure in the resulting film.

Furthermore, the polyester film of the present invention may contain, for example, an easy lubricant (fine particles), a colorant, a heat stabilizer, a nucleating agent (crystallization agent), a flame retardant and the like in addition to the light stabilizer. It can contain as.

Extruder The extruder used for melt kneading is not particularly limited, and a single screw extruder, a twin screw extruder, or the like can be used, but a twin screw extruder can be preferably used.

The twin screw extruder that can be used in the present invention will be described. FIG. 1 schematically shows an example of the configuration of a twin-screw extruder used in carrying out the method for producing a polyester film according to the present invention. FIG. 2 shows an example of a flow for carrying out the method for producing a polyester film according to the present invention.
A twin-screw extruder 100 shown in FIG. 1 is disposed around a cylinder 10 (barrel) having a supply port 12 and an extruder outlet 14, two

screws

20A and 20B rotating in the cylinder 10, and around the cylinder 10. Temperature control means 30 for controlling the temperature in the cylinder 10. In front of the supply port 12, a raw material supply device 46 is provided as shown in FIG. Further, a gear pump 44, a filter 42, and a die 40 are provided at the tip of the extruder outlet 14 as shown in FIG.

Cylinder The cylinder 10 has a supply port 12 for supplying the raw material resin and an extruder outlet 14 through which the heat-melted resin is extruded.
For the inner wall surface of the cylinder 10, it is necessary to use a material that is excellent in heat resistance, wear resistance, and corrosion resistance and that can ensure friction with the resin. Generally, nitrided steel whose inner surface is nitrided is used, but chromium molybdenum steel, nickel chromium molybdenum steel, and stainless steel can also be nitrided and used. For applications that require wear resistance and corrosion resistance in particular, a bimetallic cylinder in which a corrosion-resistant and wear-resistant material alloy such as nickel, cobalt, chromium or tungsten is lined on the inner wall surface of the cylinder 10 by centrifugal casting. It is effective to use or to form a ceramic sprayed coating on the inner wall surface of the cylinder 10.

The cylinder 10 is provided with

vents

16A and 16B for evacuation. By evacuating through the

vents

16A and 16B, volatile components such as moisture in the resin in the cylinder 10 can be efficiently removed.
The

vents

16A and 16B are required to have an appropriate opening area and number of vents in relation to the deaeration efficiency. The twin-screw extruder 100 used in the present invention desirably has one or

more vents

16A and 16B. If the number of the

vents

16A and 16B is too large, there is a concern that the molten resin may overflow from the vent and there is a concern that the staying deterioration foreign matter may increase. Therefore, it is preferable to provide one or two vents.
In addition, if the resin staying on the wall surface near the vent or the deposited volatile component falls into the extruder 100 (cylinder 10), it may be manifested as a foreign substance in the product, so care must be taken. In order to prevent stagnation, it is effective to optimize the shape of the vent lid and to select the upper and side vents appropriately. For the precipitation of volatile components, a method that prevents the precipitation by heating the piping is used. It is done.

For example, when polyethylene terephthalate (PET) is extruded, the suppression of hydrolysis, thermal decomposition, and oxidative decomposition has a great influence on the quality of the product (film).
For example, oxidative decomposition can be suppressed by evacuating the resin supply port 12 or performing a nitrogen purge.
In order to suppress resin decomposition due to shearing heat generation, it is preferable not to provide segments such as kneading as much as possible within a range in which extrusion and deaeration can be achieved at the same time.
Further, since the shear heat generation increases as the pressure at the screw outlet (extruder outlet) 14 increases, the pressure at the extruder outlet 14 is as much as possible within a range in which the degassing efficiency and the stability of the extrusion by the

vents

16A and 16B can be secured. It is preferable to make it low.

The volatile components such as moisture in the resin in the cylinder 10 can be efficiently removed by evacuating through the

vents

16A and 16B. If the vent pressure is too low, the molten resin may overflow from the cylinder 10, and if the vent pressure is too high, removal of volatile components may be insufficient, and the resulting film may be easily hydrolyzed. From the viewpoint of preventing the molten resin from overflowing the

vents

16A and 16B and selectively removing volatile components, the vent pressure is preferably 0.01 Torr to 5 Torr (1.333 Pa to 666.5 Pa). More preferably, the pressure is set at 01 Torr to 4 Torr (1.333 Pa to 533.2 Pa).

In the biaxial screw cylinder 10, two screws 20 </ b> A and 20 </ b> B that are rotated by driving means 21 including a motor and a gear are provided. As the screw diameter D increases, mass production is possible, but uneven melting tends to occur. The screw diameter D is preferably 30 to 250 mm or less, and more preferably 50 to 200 mm or less.

The twin-screw extruder 100 is roughly classified into a meshing type and a non-meshing type of the two

screws

20A and 20B, and the meshing type has a larger kneading effect than the non-meshing type. In the present invention, any of a meshing type and a non-meshing type may be used, but it is preferable to use a meshing type from the viewpoint of sufficiently mixing the raw material resin and suppressing melting unevenness.
The rotation directions of the two

screws

20A and 20B are also classified into a same direction rotation type and a different direction rotation type. The different-

direction rotating screws

20A and 20B have a higher kneading effect than the same-direction rotating type, and the same-direction rotating type has a self-cleaning effect, which is effective for preventing retention in the extruder.
Further, the axial direction of the screw also has a parallel direction and an oblique direction, and there is also a conical type shape that is used when applying strong shear.

In the twin screw extruder used in the present invention, screw segments having various shapes can be used. As the shape of the screws 20 </ b> A and 20 </ b> B, for example, a full flight screw provided with a single spiral flight 22 having an equal pitch is used.
By using a segment that imparts shear, such as a kneading disk or a rotor, in the heating and melting part, the raw material resin can be more reliably melted. Further, by using a reverse screw or a seal ring, the resin can be damped and a melt seal can be formed when evacuating through the

vents

16A and 16B. For example, as shown in FIG. 1, kneading

parts

24A and 24B that promote melting of the raw material resin as described above can be provided in the vicinity of the

vents

16A and 16B.

It is effective to provide a temperature control zone (cooling part) for cooling the molten resin in the vicinity of the exit of the extruder 100. When the heat transfer efficiency of the cylinder 10 is higher than the shear heat generation, for example, by providing a screw 28 with a short pitch in the temperature control zone (cooling section), the resin moving speed of the wall surface of the cylinder 10 is increased and the temperature control efficiency is increased. Can do.

Temperature Control Unit A temperature control unit 30 is provided around the cylinder 10. In the extruder 100 shown in FIG. 1, heating / cooling devices C1 to C9 divided into nine in the longitudinal direction from the raw material supply port 12 to the extruder outlet 14 constitute the temperature control means 30. Thus, the heating / cooling devices C1 to C9 arranged separately around the cylinder 10 are divided into, for example, heating / melting parts C1 to C7 and cooling parts C8 and C9, and the inside of the cylinder 10 is divided. Each region can be controlled to a desired temperature.

For heating, a band heater or a sheathed wire aluminum cast heater is usually used, but is not limited thereto, and for example, a heating medium circulating heating method can also be used. On the other hand, air cooling by a blower is generally used for cooling, but there is also a method of flowing water or oil through a pipe (water passage) wound around the cylinder 10.

The die outlet 10 of the die cylinder 10 is provided with a die 40 for discharging the molten resin extruded from the extruder outlet 14 into a film (strip shape). Further, a filter 42 is provided between the extruder outlet 14 of the cylinder 10 and the die 40 to prevent unmelted resin and foreign matter from entering the film.

Gear pump In order to improve the thickness accuracy, it is important to reduce the fluctuation of the extrusion amount as much as possible. A gear pump 44 may be provided between the extruder 100 and the die 40 in order to reduce the variation in the extrusion amount as much as possible. By supplying a certain amount of resin from the gear pump 44, the thickness accuracy can be improved. In particular, when using a twin screw extruder, it is preferable to stabilize the extrusion by the gear pump 44 because the pressurization capacity of the extruder itself is low.

By using the gear pump 44, the pressure fluctuation on the secondary side of the gear pump 44 can be reduced to 1/5 or less on the primary side, and the resin pressure fluctuation range can be within ± 1%. As other merits, it is possible to perform filtration with a filter without increasing the pressure at the tip of the screw, so that prevention of an increase in the resin temperature, improvement in transport efficiency, and shortening of the residence time in the extruder can be expected. It is also possible to prevent the amount of resin supplied from the screw from fluctuating with time due to the increase in the filtration pressure of the filter. However, if the gear pump 44 is installed, the length of the equipment becomes long depending on the equipment selection method, and the residence time of the resin becomes long, and the shearing stress of the gear pump section may cause the molecular chain to be broken. It is.

If the difference between the primary pressure (input pressure) and the secondary pressure (output pressure) of the gear pump 44 is excessively increased, the load on the gear pump 44 increases and shear heat generation increases. Therefore, the differential pressure during operation is within 20 MPa, preferably within 15 MPa, and more preferably within 10 MPa. In order to make the film thickness uniform, it is also effective to control the screw rotation of the extruder or to use a pressure control valve in order to keep the primary pressure of the gear pump 44 constant.

The cylinder 10 is heated by the temperature control means 30 and the screw is rotated to supply the raw material from the supply port 12. The supply port 12 is preferably cooled to prevent heat transfer from occurring in order to prevent the raw material pellets from being heated and fused, and to protect screw drive equipment such as a motor.

The raw material supplied into the cylinder 10 is melted not only by heating by the temperature control means 30 but also by heat generated by friction between the resins accompanying rotation of the

screws

20A and 20B, friction between the resin and the

screws

20A and 20B and the cylinder 10, and the like. And gradually moves toward the extruder outlet 14 as the screw rotates.
The raw material resin supplied into the cylinder 10 is heated to a temperature equal to or higher than the melting point Tm (° C.). However, if the resin temperature is too low, melting during melt extrusion may be insufficient and ejection from the die 40 may be difficult. In addition, if the resin temperature is too high, the amount of terminal carboxyl groups of the resin is remarkably increased by thermal decomposition, which may lead to a decrease in hydrolysis resistance of the film formed.

In the present invention, it is preferable to control the temperature of the cylinder 10 to 220 to 320 ° C., preferably to 280 to 300 ° C., by adjusting the heating temperature by the temperature control means 30 and the rotational speed of the

screws

20A and 20B. More preferred. If the temperature of the cylinder 10 is 220 ° C. or higher, a part of the molten resin is solidified to prevent generation of unmelted resin, and if it is 320 ° C. or lower, the terminal COOH of the resin increases due to thermal decomposition. A decrease in hydrolysis resistance of the formed film is suppressed.
It is more preferable to perform melt kneading by replacing the inside of the extruder with nitrogen in that the generation of terminal COOH due to thermal decomposition can be further suppressed.

<Film forming process>
The molten resin extruded from the extruder 100 is formed into a film to form a polyester film containing 0.1 to 2.0% by mass of a carbodiimide compound.

Cooling First, the molten resin (melt) melt-extruded from the extruder 100 is passed through the gear pump 44 and the filter 42 and extruded from the die 40 onto a cast roll (cooling roll) to be cooled.

It is preferable to adjust the humidity to 5% RH to 60% RH and to adjust to 15% RH to 50% RH from the time when the molten resin is extruded from the die 40 until it contacts the cast roll (air gap). It is more preferable. By adjusting the humidity in the air gap to the above range, it is possible to adjust the amount of COOH and OH on the film surface, and by adjusting to low humidity, the amount of carboxylic acid on the film surface can be reduced. .

The molten resin extruded from the extrusion die is cooled and solidified using a cast roll (cooling roll). If the cooling is insufficient, spherulites are likely to be generated, which causes uneven stretching and may cause uneven thickness of the film.
The temperature of the cast roll is preferably 10 ° C or higher and 80 ° C or lower, more preferably 15 ° C or higher and 70 ° C or lower, and further preferably 20 ° C or higher and 60 ° C or lower. Furthermore, from the viewpoint of improving the adhesion between the melt and the cast roll and increasing the cooling efficiency, it is preferable to apply static electricity before the melt contacts the cast roll. Furthermore, it is also preferable to promote cooling by applying cold air from the opposite surface of the cast roll or by bringing a cooling roll into contact therewith. Thereby, even a thick film can be cooled effectively.

The thickness of the resin sheet (unstretched film) cooled by the cooling roll is preferably 1000 to 4000 μm. If the thickness of the unstretched film is 1000 μm or more, the stretched film does not become too thin, and the rigidity (waist) of the film necessary for the product is maintained, and handling becomes easy. Thickness unevenness can be reduced.

Biaxial stretching The unstretched polyester film cooled by the cooling roll is stretched in the longitudinal direction (MD) and the width direction (TD) to perform biaxial stretching (longitudinal stretching and lateral stretching).

For example, the unstretched film is led to a group of rolls heated to a temperature of 70 ° C. or higher and 140 ° C. or lower, and stretched at a stretch ratio of 3 to 5 times in the longitudinal direction (longitudinal direction, that is, the traveling direction of the film), It cools with the roll group of the temperature of 20 to 50 degreeC. Subsequently, the both ends of the unstretched film are guided to a tenter while being gripped with clips, and in an atmosphere heated to a temperature of 80 ° C. or higher and 150 ° C. or lower, the direction perpendicular to the longitudinal direction (width direction) is 3 to 5 times. The film is stretched at the following stretching ratio.

The stretching rate is preferably 3 to 5 times in each of the longitudinal direction and the width direction. Moreover, it is preferable that the area magnification (longitudinal stretch magnification x lateral stretch magnification) is 9 times or more and 15 times or less. When the area magnification is 9 times or more, the reflectance, concealability, and film strength of the resulting biaxially stretched polyester film are good, and when the area magnification is 15 times or less, tearing during stretching should be avoided. Can do.

As the biaxial stretching method, as described above, any one of the sequential biaxial stretching method in which the stretching in the longitudinal direction and the width direction is separated and the simultaneous biaxial stretching method in which the stretching in the longitudinal direction and the width direction are simultaneously performed. It may be.
Further, for the purpose of improving the strength of the polyester film, stretching used for known stretched films such as multi-stage longitudinal stretching, re-longitudinal stretching, re-longitudinal and transverse stretching, and transverse-longitudinal stretching may be performed. The order of longitudinal stretching and lateral stretching may be reversed.
Moreover, after extending | stretching an unstretched film to one direction, functional layers, such as a weather resistance layer, a colored layer, an easily bonding layer, may be provided by application | coating on the surface of a film, and you may extend | stretch in another direction after that.

Heat setting In order to complete the crystal orientation of the obtained biaxially stretched film and to impart flatness and dimensional stability, the biaxially stretched film is subsequently heat-set in the tenter and uniformly cooled slowly. Then cool to room temperature. In general, when the heat setting treatment temperature (Ts) is low, the heat shrinkage of the film is large. Therefore, in order to impart high thermal dimensional stability, the heat treatment temperature is preferably high. However, if the heat treatment temperature is too high, the orientation crystallinity is lowered, and as a result, the formed film may be inferior in hydrolysis resistance.
In the present invention, when heat-setting the biaxially stretched film, the temperature is preferably 150 to 250 ° C, more preferably 180 to 240 ° C.

Thermal relaxation If necessary, a relaxation (relaxation) treatment of 1 to 12% in the width direction or the longitudinal direction may be performed.
The heat-fixed polyester film is usually cooled to Tg or less, cut the clip gripping portions at both ends of the polyester film, and wound into a roll. In this case, it is preferable to perform a relaxation treatment of 1 to 12% in the width direction and / or the longitudinal direction within a temperature range not higher than the final heat setting temperature and not lower than Tg.
In terms of dimensional stability, the cooling is preferably performed by gradually cooling from the final heat setting temperature to room temperature at a cooling rate of 1 ° C. to 100 ° C. per second. In particular, it is preferable to slowly cool Tg + 50 ° C. to Tg at a cooling rate of 1 ° C. or more and 100 ° C. or less per second. There are no particular limitations on the means for cooling and relaxation treatment, but it is preferable to perform these treatments while sequentially cooling in a plurality of temperature regions, particularly in terms of improving the dimensional stability of the polyester film.
Tg represents a glass transition temperature and can be measured based on JIS K7121 or ASTM D3418-82. For example, in the present invention, Tg is measured using a differential scanning calorimeter (DSC) manufactured by Shimadzu Corporation.
Specifically, 10 mg of a polymer such as polyester is weighed as a sample, set in an aluminum pan, and heated at a rate of temperature increase of 10 ° C./min from room temperature to a final temperature of 300 ° C., with a DSC apparatus, the amount of heat with respect to temperature Was measured as the glass transition temperature.

<Polyester film>
Through the steps as described above, a polyester film containing 0.1 to 2.0% by mass of a carbodiimide compound can be produced.
Since the polyester film produced according to the present invention contains 0.1 to 2.0% by mass of the carbodiimide compound, the sealing reaction with the carbodiimide compound proceeds even after film formation, and the film is subjected to high temperature and high humidity for a long time. High hydrolysis resistance can be exhibited. Therefore, the polyester film produced according to the present invention is suitable for electric and electronic members, and in particular, is disposed on the back surface of the solar cell polyester film, specifically on the side opposite to the solar light incident side of the solar cell module. It is suitable for uses such as a protective sheet for solar cells such as a back surface protective sheet (so-called back sheet for solar cells), a barrier film substrate and the like.

Also, the polyester material excised and recovered in the film production process can be used as a recycled polyester material after being dried under specific conditions by the method of the present invention.

<Solar cell module>
As an example of the configuration of the use of the solar cell module, a power generating element (solar cell element) connected by a lead wiring for taking out electricity is sealed with a sealing agent such as ethylene / vinyl acetate copolymer (EVA) resin. The structure obtained by sandwiching this between a transparent substrate such as glass and the polyester film (back sheet) of the present invention and sticking them together is mentioned.
Solar cell elements include silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, III-V groups such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, gallium-arsenic, and II Various known solar cell elements such as a group VI compound semiconductor can be applied.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1
As shown in Fig. 1, the twin screw extruder is equipped with a screw with the following configuration in a cylinder with two vents as shown in Fig. 1. The cylinder is divided into nine zones in the longitudinal direction around the cylinder for temperature control. A double vent type co-rotating and meshing type twin screw extruder equipped with a heater (temperature control means) that can be used was prepared.
Screw diameter D: 65mm
Length L [mm] / screw diameter D [mm]: 31.5 (width of one zone: 3.5D)
Screw shape: plasticization kneading section just before the first vent, degassing promotion kneading section just before the second vent

After the extruder exit of the twin screw extruder, as shown in FIG. 2, a gear pump, a metal fiber filter and a die having the following constitution are connected, the set temperature of the heater for heating the die is 280 ° C., and the average residence time is 10 minutes.
Gear pump: 2-gear type Filter: Sintered metal fiber filter (pore diameter 20μm)
Die: Lip spacing 4mm

Raw material Polyester terephthalate produced using Ti-citric acid complex as catalyst as polyester resin A (Intrinsic viscosity (IV): 0.78 dl / g, terminal carboxyl group content (AV): 15 eq / ton, moisture content after drying) : 41 ppm) PET pellets were prepared.
As the carbodiimide-based end-capping agent A, STABILIZER 9000 (molecular weight: about 20000, manufactured by Rhein Chemie) was prepared.
As recycled material A, a recycled chip containing 100 parts by mass of polyester resin A and 1 part by mass of end-capping agent A was prepared.
The recycled material A was contacted with dehumidified air having a dew point of −30 ° C. and an isocyanate concentration of 0.02 ppm, and dried at 160 ° C. for 7 hours. As a result, a recycled material having an intrinsic viscosity (IV): 0.62 dl / g, a terminal carboxyl group amount (AV): 13 eq / t, and a moisture content after drying: 45 ppm was obtained.

Melt extrusion The barrel temperature of the twin screw extruder was set to 290 ° C., and the screw rotation speed was set to 40 rpm. 90 parts by mass of polyester resin A, 10 parts by mass of the dried recycled material A, and 0.56 parts by mass of end-capping agent A were supplied from the supply port, heated, melted, and melt extruded. .

The melt (melt) extruded from the extruder outlet was passed through a gear pump and a metal fiber filter (pore diameter 20 μm), and then extruded from a die to a cooling (chill) roll. The extruded melt was brought into close contact with the cooling roll using an electrostatic application method. As the cooling roll, a hollow cast roll is used, and the temperature can be adjusted by passing water as a heating medium.
The conveyance area (air gap) from the die exit to the cooling roll surrounds this conveyance area, and humidity is adjusted to 30% RH by introducing humidity-conditioned air therein. By adjusting the extrusion amount of the extruder and the slit width of the die, the melt thickness was about 3300 μm on average.

Biaxial stretching Next, the obtained unstretched film was biaxially stretched. The draw ratio was longitudinal stretch: 3.4 times and transverse stretch: 4.3 times. As a result, a PET film having a thickness of 250 μm was obtained.

Evaluation The raw material and the produced PET film were evaluated by the following methods, and the results are shown in Table 1.

Terminal carboxyl group content (AV)
A 0.1 g sample was dissolved in 10 ml of benzyl alcohol, and further chloroform was added to obtain a mixed solution, to which was added a phenol red indicator. This solution was titrated with a reference solution (0.01N KOH-benzyl alcohol mixed solution), and the amount of terminal carboxyl groups (AV) was determined from the amount of the reference solution added just before the color of the phenol red indicator changed from yellow to red. .

Intrinsic viscosity (IV)
The intrinsic viscosity (IV) is a specific viscosity (η _sp = η _r −1) concentration obtained by subtracting 1 from the ratio η _r (= η / η ₀ ; relative viscosity) of the solution viscosity (η) and the solvent viscosity (η ₀ ). It is a value obtained by extrapolating a value obtained by dividing by a state where the density is zero. The intrinsic viscosity (IV) is obtained by dissolving a polyester resin in a 1,1,2,2-tetrachloroethane / phenol (= 2/3 [mass ratio]) mixed solvent using an Ubbelohde viscometer, and a solution at 25 ° C. It was determined from the viscosity.

Isocyanate gas concentration The isocyanate gas concentration in the drying process of the recycled material was measured by the following method.
The gas in the dryer was collected, the amount in the gas was quantified using gas chromatography, and the concentration was calculated.

Isocyanate / carbodiimide concentration ratio The isocyanate / carbodiimide concentration ratio in the drying step of the recycled material was determined by the following method.
The carbodiimide concentration in the recycled material before drying was measured by infrared absorption. Using samples having different carbodiimide concentrations, a calibration curve was created from the relationship with the peak intensity of 2300 cm ⁻¹ , and the measured peak intensity of the recycled material was converted to a concentration based on this calibration curve. The isocyanate concentration was similarly measured by infrared absorption. A calibration curve was prepared from the peak intensity of 2150 cm ⁻¹ , and the measured peak intensity of the recycled material was converted to the isocyanate concentration based on this calibration curve.
These concentration ratios were calculated from the concentrations of isocyanate and carbodiimide thus obtained.

Carbodiimide compound content The carbodiimide compound (unreacted component) contained in the recycled material and the produced polyester film was measured by the following method.
The carbodiimide concentration of each material and polyester film was measured by infrared absorption. Using samples having different carbodiimide concentrations, a calibration curve was created from the relationship with the peak intensity of 2300 cm ⁻¹ , and the measured peak intensity of each material and polyester film was converted to a concentration based on this calibration curve.

Confirmation of generation of gelled product The gelled product in the produced polyester film was confirmed by the following method.
The film is cut into 10 cm × 5 cm and attached to a glass plate. Using an optical microscope (× 20), the periphery of the foreign material was polarized in a crossed Nicol state, 50 fields of 5 mm × 5 mm square were confirmed, and a gelled product (transparent and nucleus could not be visually confirmed) was confirmed.

Hydrolysis resistance When the produced polyester film is subjected to wet heat treatment (heat treatment) under the conditions of 125 ° C. × 100% RH, the tensile fracture elongation retention before and after the treatment is 50%. A, where B was less than 150 hours. The tensile test was in accordance with JIS K 7127.
Breaking elongation retention [%] = (breaking elongation after heat treatment) / (breaking elongation before heat treatment) × 100

Coloring For a produced polyester film, a sample having a thickness of 200 μm is measured with a color meter (ND-101D (manufactured by Nippon Denshoku Industries Co., Ltd.)). If the transmission b value of the film is less than 2, A or 2 or more B.

Reference Examples 1 and 2 and Examples 2 to 19
A polyester film was produced and evaluated in the same manner as in Example 1 except that the raw materials and extrusion conditions were changed as shown in Tables 2 and 3.

Comparative Examples 1-10
A polyester film was produced and evaluated in the same manner as in Example 1 except that the raw materials and extrusion conditions were changed as shown in Table 4.

In addition, it is as Table 1 about each material used by the Example and the comparative example.

Carbodiimide compound Starvacol P200 (Rhein Chemie Japan Co., Ltd.) is a carbodiimide sealant having a molecular weight of about 2,000.
Cyclic carbodiimide The following compounds were used as the cyclic carbodiimide.
The cyclic carbodiimide (1) is a compound having a molecular weight of 516 described in Examples of JP 2011-258541 A, and was synthesized with reference to the synthesis method described in Reference Example 1 of JP 2011-258641 A.
Cyclic carbodiimide (2) is a compound having a molecular weight of 252 described in Examples of JP 2010-285554 A, and was synthesized with reference to the synthesis method described in Production Example 1 of JP 2010-285554 A.
The structures of these cyclic carbodiimide terminal blockers are shown below.

Production of CHDM polyester resin CHDM polyester resins (polyester resins C to L) were produced as follows.
First step: Isophthalic acid (IPA) and terephthalic acid (TPA) as dicarboxylic acid components, cyclohexanedimethanol (CHDM) and ethylene glycol (EG) as diol components, magnesium acetate and antimony trioxide as catalysts. After melting in a nitrogen atmosphere at 30 ° C., the temperature was raised to 230-250 ° C. over 3 hours with stirring, and methanol was distilled off to complete the transesterification reaction. At this time, each CHDM polyester resin was obtained by changing the addition amount of IPA, TPA, CHDM, and EG.
Second step: After completion of the transesterification reaction, an ethylene glycol solution in which phosphoric acid was dissolved in ethylene glycol was added.
Third step: The polymerization reaction was performed at a final temperature of 285 to 310 ° C. and a degree of vacuum of 0.1 Torr to obtain a polyester, which was pelletized.
Step 4: For some levels, the polyester pellets obtained above were dried and crystallized at 160 ° C. for 6 hours.

For the CHDM polyester resin obtained above, the cyclohexanedimethanol content in the diol component and the isophthalic acid content in the dicarboxylic acid component were measured by the following methods.

Composition Measurement Method The obtained CHDM polyester pellets were dissolved in hexafluoroisopropanol (HFIP) and then quantified by ¹ H-NMR. Standard samples (CHDM, terephthalic acid, EG, isophthalic acid) were measured in advance, and signals were identified using this.
The amount of the isophthalic acid residue obtained and the amount of the CHDM residue are shown in Table 1. The 100 mol% -isophthalic acid content (mol%) is the terephthalic acid content (mol%), and the 100 (mol%)-CHDM ratio (mol%) is the EG content (mol%).
Some of these levels were dried and then subjected to solid state polymerization in a nitrogen stream at 200 to 240 ° C. for 24 hours.
The IV and AV of these CHDM polyester resins were measured by the above method. The results are shown in Table 1.

In Examples 1 to 19, a polyester film equivalent to Reference Examples 1 and 2 in which no recycled material was used with respect to gelation, hydrolysis resistance, and coloring could be produced at low cost.

In Comparative Example 1, the drying temperature (190 ° C.) of the recycled material is high, the carbodiimide compound contained in the recycled material is decomposed to increase the concentration of the isocyanate gas, and the carbodiimide compound in the recycled material is deactivated. The hydrolysis resistance of the finished polyester film is reduced. In addition, it is considered that the polyester film of Comparative Example 1 was colored and a gelled product was generated by the reaction between the carbodiimide compounds.

In Comparative Example 2, the concentration of isocyanate gas used for drying the recycled material was too high, and the resulting second carbodiimide compound was deactivated. As a result, the carbodiimide compound present in the film was reduced and produced. In the polyester film, it is considered that the hydrolysis resistance decreased, the gelled product was generated, and the coloring was increased.

In Comparative Example 3, it is considered that the isocyanate concentration used for drying the recycled material was too low, the amount of residual carbodiimide in the recycled material was increased, gelled products were generated in the extrusion process, and the coloring of the polyester film was increased.

In Comparative Example 4, the amount of moisture in the atmosphere for drying the recycled material (dew point: −10 ° C.) becomes too great, and both the isocyanate gas and carbodiimide are deactivated, and the remaining amount of the end-capping agent contained in the recycled material It is considered that the hydrolysis resistance performance of the polyester film was lowered due to the decrease in the thickness.

In Comparative Example 5, it is considered that the drying temperature (120 ° C.) of the recycled material is too low, the amount of water present in the recycled material is increased, the isocyanate or carbodiimide compound is deactivated, and the end-capping effect is decreased. It is done.

In Comparative Example 6, it is considered that the amount of the end-capping agent was too much to generate a gelled product, and coloring of the produced polyester film was increased.

In Comparative Example 7, it is considered that the coloring of the polyester film produced due to the excessive amount of the recycled material was increased.

In Comparative Example 8, since the viscosity of the polyester resin was lowered, the amount of terminal carboxyl groups increased, and as a result, the amount of added end-capping agent increased. However, since the viscosity of the base is also lowered, it is considered that the physical properties of the produced polyester film are lowered and the hydrolysis resistance is also lowered.

In Comparative Examples 9 and 10, since the copolymerization ratio of the polyester resin is high, it is considered that the crystallinity was lost and the film could not be formed because it could not be normally dried.

The disclosure of Japanese Patent Application No. 2012-170023 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims

The recycled polyester material containing the first carbodiimide compound is dried by contacting with an air or an inert gas having a dew point of −25 ° C. or less and an isocyanate concentration of 0.01 ppm to 100 ppm to dry the first polyester. A recycling material drying step for deactivating the carbodiimide compound;
A melt extrusion process in which 50 to 95 parts by mass of a polyester resin, 5 to 50 parts by mass of the dried recycled polyester material, and a raw material containing a second carbodiimide compound are melt-kneaded by an extruder to extrude the molten resin;
A film forming step of forming a polyester film having a total content of carbodiimide compounds of 0.1 to 2.0% by mass by molding the molten resin extruded from the extruder into a film;
The manufacturing method of the polyester film which has this.
The method for producing a polyester film according to claim 1, wherein the recycled polyester material is dried at 135 to 180 ° C in the recycling material drying step.
The terminal carboxyl group amount (AV) of the recycled polyester material is 3 to 20 equivalent / ton, and the terminal carboxyl group amount (AV) of the polyester resin is 3 to 55 equivalent / ton. A method for producing a polyester film.
At least one of the polyester resin and the recycled polyester material includes a structure derived from 1,4-cyclohexanedimethanol in an amount of 0.1 to 20 mol% or 80 to 100 mol% based on the total structure derived from the diol component. The method for producing a polyester film according to any one of claims 1 to 3, comprising 1,4-cyclohexanedimethanol-based polyester.
At least one of the first carbodiimide compound contained in the recycled polyester material and the second carbodiimide compound contained in the raw material has one carbodiimide group, and the first nitrogen and the second nitrogen are bound by a bonding group. The method for producing a polyester film according to any one of claims 1 to 4, which is a cyclic carbodiimide compound containing a bonded cyclic structure.
The method for producing a polyester film according to claim 5, wherein the cyclic carbodiimide compound is at least one selected from compounds represented by the following formulas (2) to (4).

Wherein (2), Q a is an aliphatic group, an alicyclic group, an aromatic group or a divalent linking group which is a combination of these, it may contain a heteroatom.

Wherein (3), Q b is an aliphatic group, an alicyclic group, an aromatic group or a trivalent linking group combinations thereof, and may contain a hetero atom. Y represents a carrier supporting a cyclic structure.

In formula (4), Q c is any one tetravalent linking group selected from the group consisting of an aliphatic group, an alicyclic group, and an aromatic group, or an aliphatic group, an alicyclic group, And a tetravalent linking group that is a combination of two or more groups selected from the group consisting of aromatic groups, and may further have a heteroatom. Z 1 and Z 2 each independently represent a carrier carrying a cyclic structure, and may be bonded to each other to form a cyclic structure.
A polyester film produced by the method for producing a polyester film according to any one of claims 1 to 6.
A solar cell protective sheet comprising the polyester film according to claim 7.
A solar cell module comprising the solar cell protective sheet according to claim 8.