JP2014088547A - Polyethylene terephthalate film and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film excellent in moist heat resistance, flatness, and heat resistance, and a method for manufacturing the same.SOLUTION: A polyethylene terephthalate film satisfies the following (1) and (2): (1) the crystallization temperature (Tc) of polyethylene terephthalate composing a film is 145°C or more and 160°C or less and the peak width of the crystallization temperature (Tc) is 10°C or more and 25°C or less; and (2) when the polyethylene terephthalate film is measured by Fourier transform infrared spectroscopy, a ratio R1 of a spectral intensity r1 observed at 1388 cmto a spectral intensity r2 observed at 1372 cmsatisfies formula (i) and a ratio R2 of a spectral intensity r3 observed at 988 cmto a spectral intensity r4 observed at 971 cmsatisfies formula (ii): (i) 0.70≤R1≤0.94 and (ii) 0.60≤R2≤0.73, wherein R1=r1/r2 and R2=r3/r4.

Description

The present invention relates to a polyethylene terephthalate film excellent in wet heat resistance, flatness and heat resistance, and a method for producing the same.

  Polyester (especially polyethylene terephthalate, polyethylene 2,6-naphthalene dicarboxylate, etc.) resins are excellent in mechanical properties, thermal properties, chemical resistance, electrical properties, and moldability, and are used in various applications. Polyester films made from the polyester resin, especially biaxially oriented polyester films, are used for solar battery back sheets, water heater motors, car air conditioners, etc. due to their mechanical and electrical characteristics. It is used as various industrial materials such as electrical insulating materials, magnetic recording materials, capacitor materials, packaging materials, building materials, photographic applications, graphic applications, thermal transfer applications used for motors and drive motors.

  Among these applications, electrical insulating materials (such as solar cell backsheets) are often used in harsh environments for a long time, and polyester resins are brittle due to a decrease in molecular weight and an increase in crystallinity due to hydrolysis. Since the mechanical properties and the like are deteriorated due to the progress of the process, when it is used in a harsh environment for a long period of time, improvement in heat and humidity resistance is required. (Patent Documents 1, 2, and 3). In general, hydrolysis of a polyester in a moist and hot atmosphere proceeds using the terminal carboxyl group of the polyester as a self-acid catalyst, and as a result of hydrolysis of the polyester, the amount of the terminal carboxyl group further increases. As the amount of terminal carboxyl groups increases, hydrolysis proceeds more. Therefore, in order to improve wet heat resistance, it is necessary to suppress an increase in the amount of terminal carboxyl groups in a moist heat atmosphere. In Patent Documents 1 and 2, by adding phosphoric acid and alkali metal phosphate, the increase in the amount of terminal carboxyl groups of the polyester in a moist heat atmosphere is suppressed, and the wet heat resistance of the film made of the polyester composition is improved. Technology is being considered. Even in Patent Document 3, by adding phosphoric acid and alkali metal phosphate, it is possible to suppress an increase in the amount of terminal carboxyl groups of the polyester in a moist heat atmosphere, and further improve the film forming conditions to improve the heat and moisture resistance. Is being considered.

  Moreover, when using it for the compressor motor use for air-conditioners among electrical insulating materials, since it is used in the environment where it becomes high temperature with compression and expansion of a refrigerant | coolant, the heat resistance of a film is also requested | required.

  In addition, in recent years, hydrofluorocarbon (HFC) has been widely used as a refrigerant for air conditioners instead of hydrochlorofluorocarbon (HCFC) from the environmental aspect (Patent Document 4). The refrigerant R32 represented by HFC has been pointed out that the operating environment temperature of the compressor is higher than before due to its thermal characteristics, and heat resistance requirements for films used for compressor motor applications for air conditioners. Is growing.

JP 2010-248492 A International Publication No. 2010/103945 Pamphlet JP 2012-56158 A Special table 2011-525204 gazette

  In the polyester films described in Patent Documents 1 to 3, an increase in the amount of terminal carboxyl groups in a wet heat atmosphere can be suppressed to some extent, but the effect is not sufficient. Further, when these polyester films are used for applications such as solar battery back sheet films that are exposed to the outdoors for a long period of time, there is a problem in that hydrolysis eventually proceeds and mechanical properties cannot be maintained. Moreover, since the thermal characteristics of the film are not sufficient, there is a problem that the flatness is deteriorated in the film forming process. Also, regarding heat resistance, it was not able to withstand the use of compressor motors for air conditioners.

  As a result of intensive studies on the problem, the present inventors set the crystallization temperature (Tc) of the polyethylene terephthalate constituting the film to a constant temperature, and the peak width of the crystallization temperature (Tc) to a certain range. The present inventors have found that the above problem can be solved by setting the molecular chain structure to a specific structure.

  That is, the subject of this invention is providing the polyethylene terephthalate film which expresses sufficient moisture-and-heat resistance, flatness, and heat resistance in view of this prior art, and its manufacturing method.

In order to solve the above problems, the present invention has the following configuration. That is,
[I] A polyethylene terephthalate film satisfying (1) and (2).
(1) Crystallization temperature (Tc) in differential scanning calorimetry (DSC) of polyethylene terephthalate constituting the film is 145 ° C. or more and 160 ° C. or less, and the crystallization temperature (Tc) peak width is 10 ° C. or more and 25 ° C. or less. Be.
(2) The ratio R1 of the spectral intensity r1 observed at 1388 cm ⁻¹ and the spectral intensity r2 observed at 1372 cm ⁻¹ when the polyethylene terephthalate film was measured by Fourier transform infrared spectroscopy (FT-IR). satisfied but the formula (i), and the spectral intensity r3 observed at 988cm ^-1, the ratio R2 of the spectral intensity r4 observed at 971cm ^-1 is (ii) satisfying the formula.
(I) 0.70 ≦ R1 ≦ 0.94
(Ii) 0.60 ≦ R2 ≦ 0.73
However, R1 = r1 / r2, R2 = r3 / r4
[II] The polyethylene terephthalate film according to [I], wherein the polyethylene terephthalate constituting the polyethylene terephthalate film has a diethylene glycol content of 0.7 wt% or more and 2.0 wt% or less.
[III] The polyethylene terephthalate film according to [I] or [II], which satisfies (3) to (5).
(3) The polyethylene terephthalate constituting the film contains one or more metal elements of manganese element and calcium element, and the content thereof is 0.6 mol / t or more and 11.2 mol / t or less with respect to polyethylene terephthalate. There is.
(4) The polyethylene terephthalate constituting the film contains a phosphorus element.
(5) M1 (mol / t) content of alkali metal element relative to polyethylene terephthalate constituting the film, manganese element content (mol / t) and calcium element content (mol / t) relative to polyethylene terephthalate constituting the film Is the metal content M in the polyethylene terephthalate obtained by the following formula (iii), where M2 (mol / t) and the content of phosphorus element relative to the polyethylene terephthalate constituting the film are P (mol / t). (Mol / t) and the phosphorus element content P (mol / t) satisfy the following formula (iv).
(Iii) M = (M1) / 2 + M2
(Iv) 1.1 ≦ M / P ≦ 2.0
[IV] From [I], the intrinsic viscosity (IV) of the polyethylene terephthalate constituting the film is 0.65 dl / g or more and 0.80 dl / g or less, and the terminal carboxyl group amount is 1 equivalent / t or more and 25 equivalent / t or less. The polyethylene terephthalate film according to any one of [III].
[V] The method for producing a polyethylene terephthalate film according to any one of [I] to [IV], including the following steps (6) to (8):
(6) Biaxial stretching step of biaxial stretching at an area magnification of 13.5 times or more in the longitudinal direction (MD) of the film and the width direction (TD) of the film at a temperature T1n (° C.) satisfying the following formula (v) .
(V) Tg ≦ T1n ≦ Tg + 40
Tg: Glass transition temperature (° C.) of polyethylene terephthalate constituting the film
(7) A first heat treatment step in which heat treatment is performed at the heat treatment temperature Th1 (° C.) satisfying the following formula (vi) after the step (6).
(Vi) Tm−90 ≦ Th1 ≦ Tm−45
Tm: melting point (° C.) of polyethylene terephthalate constituting the film
(8) After the step (7), at a heat treatment temperature Th2 (° C.) satisfying the following formula (vii), the film length direction (MD) and film width direction ( TD) Second heat treatment step in which both shrink by 1% to 10%.
(Vii) Tc ≦ Th2 ≦ Th1
Tc: Crystallization temperature of polyethylene terephthalate constituting the film (° C.)

  According to the present invention, it is possible to provide a polyethylene terephthalate film having high heat resistance and high heat resistance over a long period of time. Furthermore, by using such a film, it is possible to provide a film for a solar battery back sheet having high heat-and-moisture resistance and a compressor motor film for an air conditioner having excellent heat resistance.

  The polyethylene terephthalate film used in the present invention needs to be a polyethylene terephthalate in which the resin constituting the film is mainly composed of terephthalic acid and ethylene glycol from the viewpoint of mechanical properties, crystallinity, and heat and humidity resistance. In addition, in this specification, a structural component shows the minimum unit which can be obtained by hydrolyzing polyester. In the present invention, polyethylene terephthalate containing terephthalic acid and ethylene glycol as main constituents means that the proportion of terephthalic acid constituents in all dicarboxylic acid constituents is 90 mol% or more and 100 mol% or less, and ethylene in all diol constituents A resin having a glycol constituent component ratio of 90 mol% or more and 100 mol% or less is represented. If the proportion of the terephthalic acid constituent component is less than 90 mol% and / or the proportion of the ethylene glycol constituent component is less than 90 mol%, the mechanical properties are lowered or the crystallinity is lowered and the heat and humidity resistance is lowered. The proportion of the terephthalic acid constituent component in all the dicarboxylic acid constituent components is preferably 95 mol% or more and 100 mol% or less. Moreover, the ratio of the ethylene glycol constituent component in all the diol constituent components is preferably 95 mol% or more and 100 mol% or less.

  The polyethylene terephthalate film used in the present invention may contain a copolymer component other than terephthalic acid and ethylene glycol as long as necessary characteristics are not lost. As copolymer components, dicarboxylic acid components include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, dimer acid, eicosandioic acid, pimelic acid, azelaic acid, methylmalon Aliphatic dicarboxylic acids such as acid, ethylmalonic acid, adamantane dicarboxylic acid, norbornene dicarboxylic acid, isosorbide, cyclohexane dicarboxylic acid, decalin dicarboxylic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid Acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-sodium sulfoisophthalic acid , Phenylenda Dicarboxylic acids, anthracene dicarboxylic acid, phenanthrene carboxylic acid, 9,9'-bis (4-carboxyphenyl) dicarboxylic acids such as fluorene acids and aromatic dicarboxylic acids, or include an ester derivative thereof. Examples of the diol component include aliphatic diols such as 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol, cyclohexane Alicyclic diols such as dimethanol, spiroglycol, isosorbide, bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, 9,9'-bis (4-hydroxyphenyl) fluorene, aromatic Examples include, but are not limited to, diols such as diols, and those in which a plurality of the above diols are linked.

  The polyethylene terephthalate constituting the film of the present invention has a crystallization temperature (Tc) obtained by differential scanning calorimetry (DSC) of 145 ° C. or more and 160 ° C. or less, and a crystallization temperature (Tc) peak width of 10 ° C. or more. It is necessary to be 25 ° C. or lower. The crystallization temperature (Tc) referred to in the present invention is a measurement method described later according to JIS K7121 (1999), and is heated from 25 ° C. to 300 ° C. at a rate of 30 ° C./min. Differential scanning calorimetry at the time of the second temperature increase obtained by holding for a minute and then rapidly cooling to 25 ° C. or lower and then increasing the temperature from 25 ° C. to 300 ° C. at a temperature increase rate of 30 ° C./min. It represents the temperature at the peak top of the crystallization peak, which is an exothermic peak observed on a chart (the vertical axis is thermal energy and the horizontal axis is temperature). When a plurality of exothermic peaks are observed, the average value of the peak top temperatures is defined as the crystallization temperature. In addition, the width of the crystallization temperature (Tc) peak represents the absolute value of the difference between the extrapolation crystallization start temperature (Tic) and the extrapolation crystallization end temperature (Tec) obtained by a measurement method described later. It is particularly important from the viewpoint of heat and humidity resistance that the Tc and Tc peak widths fall within the above ranges. When the crystallization temperature (Tc) is higher than 160 ° C., the flatness deteriorates in the heat treatment step after stretching. On the other hand, when the crystallization temperature (Tc) is less than 145 ° C., crystallization in the stretching step becomes remarkable, and the stretchability is lowered. More preferably, Tc is 148 ° C. or higher and 155 ° C. or lower, and the Tc peak width is 16 ° C. or higher and 22 ° C. or lower.

  The width of the crystallization temperature (Tc) peak represents the responsiveness of the structural change of the polyethylene terephthalate molecular chain constituting the film to heat. The narrower the peak width, the higher the responsiveness. In order to form a structure necessary for the present invention to be described later, since the crystallization temperature (Tc) peak width exceeds 25 ° C., the responsiveness of the structural change of the polyethylene terephthalate molecular chain constituting the film to heat is not sufficient. Long heat treatment is required. If the film is heat-treated at a temperature exceeding the crystallization temperature (Tc) for a long time, the flatness of the film is deteriorated. Moreover, as a result of the Gauche structure generated by the structural change receiving further heat, the Gauche structure is changed to a trans structure derived from a thermodynamically stable crystal portion, and the structure necessary for the present invention described later cannot be formed. Inferior to moisture and heat resistance. On the other hand, if the width of the crystallization temperature (Tc) peak is less than 10 ° C., the heat responsiveness is too high, and the structural change occurs abruptly, so that the stretchability deteriorates.

  When the polyethylene terephthalate constituting the film of the present invention has a content of diethylene glycol (hereinafter sometimes referred to as DEG) of 0.7 wt% or more and 2.0 wt% or less, which is obtained by a measurement method described later, It is preferable because the Tc peak width can be easily within the above range. In the present invention, the amount of DEG contained in polyethylene terephthalate is determined by the measurement method described later, and includes both DEG copolymerized with polyethylene terephthalate molecular chains and those contained alone in polyethylene terephthalate. . When DEG is present as a copolymerization component in the polyethylene terephthalate molecular chain, the mobility of the ethylene terephthalate molecular chain is affected. In addition, when DEG is contained alone in polyethylene terephthalate, DEG exists between the molecular chains of the polymer, but DEG, which is a low molecular weight substance, is sensitive to heat. It moves actively between them, affecting the mobility of polymer molecular chains. Since molecular chain mobility greatly affects the thermal properties of polyethylene terephthalate film, DEG present in polyethylene terephthalate affects the thermal properties of polyethylene terephthalate film. As a result, the widths of Tc and Tc peaks of polyethylene terephthalate film are It is possible to be in the range.

Polyethylene terephthalate film of the present invention is measured by a measuring method described later, the spectral intensity r1 observed at 1388cm ^-1 in the Fourier transform infrared spectroscopy (FT-IR) of the polyethylene terephthalate film, to 1372cm ^-1 the ratio R1 of the spectral intensity r2 observed satisfies the formula (i), and meet the spectral intensity r3 observed at 988cm ^-1, the ratio of the spectral intensity r4 observed at 971cm ^-1 R2 is a (ii) formula There is a need.
(I) 0.70 ≦ R1 ≦ 0.94
(Ii) 0.60 ≦ R2 ≦ 0.73
However, R1 = r1 / r2, R2 = r3 / r4.

  In general, it is known that polyethylene terephthalate takes two types of conformation of the methylene group portion of polyethylene terephthalate: a Gauche structure and a trans structure. Of these two types, the trans structure is advantageous over the Gauche structure when the molecular chains are regularly arranged. From this, the Gauche structure reflects the part where the polyethylene terephthalate molecular chains are not regularly arranged (hereinafter referred to as amorphous parts), and the trans structure reflects the structure where the polyethylene terephthalate molecular chains are regularly arranged. . A structure in which molecular chains are regularly arranged includes a part forming a crystal structure (hereinafter referred to as a crystalline part) and an amorphous part in which molecular chains are arranged in the middle of the amorphous part and the crystalline part (hereinafter referred to as an oriented amorphous part). These can be observed with FT-IR. That is, r1 reflects the trans structure derived from the crystal part, r2 reflects the Gauche structure derived from the amorphous part, r3 reflects the trans structure derived from the crystal part, and r4 reflects the oriented amorphous structure. Reflects the trans-type structure derived from the part. R1 and R2 indicate that the smaller the number, the more amorphous parts in the polyethylene terephthalate film. In particular, the smaller R1, the more amorphous parts of the Gauche structure.

  When the polyethylene terephthalate film is placed in a humid heat atmosphere, the carbonyl group of the ester bond is hydrolyzed by the nucleophilic attack of water molecules, and the molecular chain is cleaved to cause deterioration. Here, when polyethylene terephthalate has a Gauche type structure, since carbonyl groups are close to each other, steric hindrance is large, and it becomes difficult for water molecules to approach the carbonyl group portion. As a result, in the polyethylene terephthalate film having a large Gauche type structure (the value of R1 is small), hydrolysis is suppressed, and the heat and moisture resistance of the film is improved. On the other hand, when a polyethylene terephthalate film is placed in a moist heat atmosphere, moisture (water vapor) penetrates between the molecules of the amorphous part having a low density and enters the inside of the film to promote hydrolysis, so that there are many amorphous parts. Too much hydrolysis cannot be suppressed.

  In general, when a polyethylene terephthalate film is placed in a moist heat atmosphere, hydrolysis proceeds and crystallization also progresses, and embrittlement is promoted. As the embrittlement progresses, the mechanical elongation decreases. When the mechanical elongation is lowered, the film is broken even by a slight impact, and when used for a solar battery back sheet or the like, the solar battery cannot be protected. Moreover, when used as an electrical insulating material for a compressor motor of an air conditioner or the like, the insulating property cannot be maintained, which is not preferable. When there are few crystal parts of a polyethylene terephthalate film, since progress of embrittlement will be suppressed, heat-and-moisture resistance and heat resistance will improve. Furthermore, since the mechanical strength of the film is derived from the crystal part in which the molecular chains are regularly arranged, and the mechanical elongation is derived from the amorphous part, the more the oriented amorphous part having both properties is, the mechanical characteristics, Excellent heat and moisture resistance.

  When a polyethylene terephthalate film is placed in a high temperature atmosphere, the polyethylene terephthalate is oxidized and deteriorated to generate radicals. Then, the generated radicals attack the carbonyl group of the ester bond by nucleophilic attack, whereby the molecular chain is broken and the deterioration proceeds. Here, when the polyethylene terephthalate has a Gauche type structure, since the carbonyl groups are close to each other, the steric hindrance is large, and it is difficult for the generated radical to approach the carbonyl group portion. As a result, in the polyethylene terephthalate film having a large Gauche structure (the value of R1 is small), the molecular chain breakage is suppressed, and the heat resistance of the film is improved.

  When R1 exceeds 0.94, since there is little Gauche type structure, it is inferior in heat-and-moisture resistance. When R1 is less than 0.70, the amorphous part is excessively increased, and the mechanical properties are deteriorated, which is not preferable. On the other hand, when R2 exceeds 0.73, the number of crystal parts increases and the heat and humidity resistance is poor. If R2 is less than 0.60, the number of oriented amorphous parts increases, and both mechanical properties and heat-and-moisture resistance deteriorate, such being undesirable.

The polyethylene terephthalate film of the present invention can be obtained by a conventionally known production method, but a polyethylene terephthalate film having a spectral intensity at FT-IR within the above range by producing a stretching and heat treatment step under the following conditions. Can be obtained stably. That is, it is preferably obtained by a production method including the following (6) to (8) stretching and heat treatment steps.
(6) A biaxial stretching process in which biaxial stretching is performed at an area magnification of 13.5 times or more in the longitudinal direction (MD) of the film and the width direction (TD) of the film at a temperature T1n satisfying the following formula (v).
(V) Tg ≦ T1n ≦ Tg + 40
Tg: Glass transition temperature (° C.) of polyethylene terephthalate constituting the film
(7) A first heat treatment step in which heat treatment is performed at the heat treatment temperature Th1 that satisfies the following formula (vi) after the step (6).
(Vi) Tm−90 ≦ Th1 ≦ Tm−45
Tm: melting point (° C.) of polyethylene terephthalate constituting the film
(8) Second heat treatment in which both MD and TD contract by 1% to 10% at a heat treatment temperature Th2 satisfying the following formula (vii) after the step of (7) for a time of 70 seconds to 600 seconds: Process.
(Vii) Tc ≦ Th2 ≦ Th1
Tc: Crystallization temperature of polyethylene terephthalate constituting the film (° C.)
When the polyethylene terephthalate film of the present invention has a single film configuration, dried raw materials (polyethylene terephthalate composition, etc.) are heated and melted in an extruder as necessary, and extruded from a die cooled onto a cast drum to be processed into a sheet. A method (melt cast method) can be used. As another method, the raw material is dissolved in a solvent, and the solution is extruded from a die onto a support such as a cast drum or an endless belt to form a film, and then the solvent is dried and removed from the film layer to form a sheet. A method (solution casting method) or the like can also be used.

  When the film is produced by the melt casting method, the dried raw material is melt-extruded from the die into a sheet using an extruder, and solidified by cooling and solidifying by static electricity on a drum cooled to a surface temperature of 10 ° C. or more and 60 ° C. or less, An unstretched sheet is produced. The polyethylene terephthalate film of the present invention can be obtained by biaxially stretching this unstretched sheet.

  When performing melt extrusion in an extruder, it is better that the time from melting in a nitrogen atmosphere to supplying chips to the extruder and extruding with a die is as short as possible. As a guideline, it is 30 minutes or less, more preferably 15 minutes. In the following, it is more preferable to set it to 5 minutes or less from the viewpoint of suppressing increase in the amount of terminal carboxyl groups.

The obtained unstretched sheet is preferably biaxially stretched under the condition (6).
(6) Biaxially stretching at an area magnification of 13.5 times or more in the longitudinal direction (MD) of the film and the width direction (TD) of the film at a temperature T1n satisfying the following expression (v).
(V) Tg ≦ T1n ≦ Tg + 40
Tg: Glass transition temperature (° C.) of polyethylene terephthalate constituting the film
As a method of biaxial stretching, in addition to a sequential biaxial stretching method in which stretching in the longitudinal direction (MD) of the film and stretching in the width direction of the film (direction perpendicular to the longitudinal direction of the film, TD) is performed, the longitudinal direction Examples thereof include a simultaneous biaxial stretching method in which stretching in the direction and the width direction is simultaneously performed. When the stretching temperature (T1n) is Tg or less, stretching cannot be performed, and when the stretching temperature exceeds Tg + 40 ° C., the film may not be sufficiently oriented, which is not preferable. If the area magnification is less than 13.5 times, the oriented amorphous portion is not sufficiently formed, and R2 becomes large, so that the heat and moisture resistance and mechanical properties may be inferior. In the case of using the sequential biaxial stretching method as the biaxial stretching method, after stretching in the longitudinal direction (MD) of the film and then stretching in the width direction (TD) of the film, the width direction (TD) of the film This is preferable because it is easy to impart orientation to the direction. At this time, when the stretching temperature in the longitudinal direction (MD) of the film is T11 (° C.) and the stretching temperature in the width direction (TD) of the film is T12 (° C.), Tg ≦ T11 ≦ T12 ≦ Tg + 40 It is preferable because the film can be efficiently oriented and the oriented amorphous portion can be sufficiently formed.

Next, it is preferable to heat-fix the obtained biaxially stretched polyethylene terephthalate film under the conditions of (6) and (7) to complete the crystal orientation of the film and to impart flatness and heat-and-moisture resistance. .
(7) A first heat treatment step in which heat treatment is performed at a temperature Th1 that satisfies the following formula (vi) after the step (6).
(Vi) Tm−90 ° C. ≦ Th1 ≦ Tm−45
(Here, the melting point (° C.) of polyethylene terephthalate constituting the film, Th1 is the heat treatment temperature (° C.)).

  If Th1 is lower than Tm-90 ° C, the flatness of the film may be deteriorated. On the other hand, if Th1 is higher than Tm-45 ° C., the crystallization of the film proceeds excessively, the film structure cannot be controlled in the step (7), and the moisture and heat resistance of the film may deteriorate. It is preferable to perform the heat treatment at a temperature Th1 that satisfies the formula (vi) because a film having good flatness and heat-and-moisture resistance can be obtained. Moreover, it is preferable from the point of the flatness of a film, and heat-and-moisture resistance that the heat processing time in the temperature of Th1 is 1 second or more and 30 seconds or less. Moreover, in the said heat processing process, you may perform a 3-12% relaxation process in the width direction or a longitudinal direction as needed.

(8) After the step of (7), the obtained polyethylene terephthalate film is subjected to a heat treatment temperature Th2 satisfying the following formula (vii) at a time of 70 seconds to 600 seconds, in the longitudinal direction (MD) of the film, Second heat treatment step (vii) Tc ≦ Th2 ≦ Th1 for shrinking in the width direction (TD) of the film by 1% to 10%
In the second heat treatment step, if the heat treatment temperature is high and the equation (vii) is not satisfied, the number of crystal parts increases and R2 increases, so that crystallization in a moist and hot atmosphere is promoted and the heat and heat resistance is poor. When the heat treatment temperature is low and (vii) is not satisfied, the formation of the amorphous part and the oriented amorphous part is not sufficiently promoted, and R1 and R2 may increase. The heat treatment temperature Th2 in the second heat treatment step is set to a temperature not lower than Tc and not higher than Th1 of the film so as to control the mobility of the molecular chain so that the structure of the oriented amorphous portion and the crystal portion is within a suitable range. Can be controlled.

  When the polyethylene terephthalate constituting the film of the present invention has Tc and Tc peak widths satisfying the thermal characteristics of [1] (1), the molecular chain of polyethylene terephthalate constituting the film through the step (8) By making the structure in the preferred arrangement, R1 can be brought into a preferred range, and a film having excellent moisture and heat resistance can be obtained.

  When the Tc of the polyethylene terephthalate constituting the film of the present invention is higher than 160 ° C., the temperature difference between Th2 and Tm is small, so that even if the heat treatment is performed for a short time, the planarity may deteriorate when the heat treatment is performed. is there.

  The width of the Tc peak represents the responsiveness of the structural change of the polyethylene terephthalate molecular chain constituting the film with respect to heat. The narrower the peak width, the higher the responsiveness. Since the film after the step (7) has many oriented amorphous parts and crystal parts, it is in a tension state in which molecular chains are regularly arranged. The step (8) is important for releasing the tension state and forming the amorphous portion from the oriented amorphous portion and the crystalline portion. By increasing the responsiveness of the film to heat, the formation of an amorphous part can be promoted in the step (8), and R1 and R2 can be in a preferred range. When the width of the Tc peak exceeds 25 ° C., the responsiveness of the structural change of the polyethylene terephthalate molecular chain constituting the film to heat is not sufficient, and a long-time heat treatment is required. When the film is heated at a temperature exceeding Tc for a long time, the flatness of the film is deteriorated. In addition, when the heat treatment is performed for a long time, the Gauche structure generated by the structural change is further subjected to heat. As a result, the Gauche structure is changed to a trans structure derived from a thermodynamically stable crystal portion, and the values of R1 and R2 are increased. Inferior to heat. If the width of the Tc peak is less than 10 ° C., the responsiveness to heat is too high, and the structural change occurs abruptly, so that the stretchability deteriorates.

  In the second heat treatment step, the heat treatment time at the temperature of Th2 is preferably 70 seconds or more and 600 seconds or less. If the heat treatment time is less than 70 seconds, the structural change cannot be sufficiently caused, the value of R1 becomes large, and the heat and moisture resistance may be inferior. On the other hand, when the time is longer than 600 seconds, the values of R1 and R2 increase, so that the heat and humidity resistance is inferior and the flatness of the film may be deteriorated. More preferably, it is 90 seconds or more and 400 seconds or less, and more preferably 120 seconds or more and 300 seconds or less.

  Moreover, in this invention, when heat-processing at the temperature of Th2, it is preferable to shrink | contract a film 1% or more and 10% or less in the longitudinal direction (MD) of a film and the width direction (TD) of a film. By contracting the film, the molecular chain in the tensioned state after step (7) can be unraveled, and the values of R1 and R2 can be effectively within a preferable range. More preferably, it is 2% or more and 5% or less.

  The film of this invention can be made into the polyethylene terephthalate film excellent in heat-and-moisture resistance, for example by manufacturing by the method of including the process of said (6), (7), (8) in this order.

  In addition, although the polyethylene terephthalate film obtained by this invention needs to have the thermal characteristics which satisfy | fill the above-mentioned [1] (1), it was mentioned above in the stage of the polyester raw material before melt-extruding to a film [ 1] It does not have to have the thermal characteristics of (1). For example, a film satisfying the above-mentioned [I] (1) can be obtained by melt-extruding polyethylene terephthalate containing a specific amount of DEG and passing through a stretching step and a heat setting step under the conditions satisfying the steps (6) and (7). can get. This is considered to be due to the fact that DEG is uniformly dispersed between the molecular chains of polyethylene terephthalate during the stretching process and the heat setting process under the conditions that satisfy the processes (6) and (7). Thus, a polyethylene terephthalate film excellent in wet heat resistance and flatness can be obtained by heat-treating the polyethylene terephthalate film that has undergone the steps (6) and (7) under the conditions that satisfy the step (8).

  Moreover, it is preferable that the polyethylene terephthalate which comprises the film of this invention contains 1 or more types of metal elements chosen from manganese and calcium from a viewpoint of a thermal characteristic improvement. The metal element in the present invention includes not only atoms but also those existing in the film in an ionic state. In general, the metal element exists in an ionic state in the film. Manganese and calcium elements present in an ionic state interact with the ether bond portion of DEG present in the film to form a complex. This complex becomes a crystal nucleus and lowers the Tc of the film. If the total content of manganese and calcium elements is less than 0.6 mol / t, the effect as a crystal nucleus is not sufficient. When the total content of manganese and calcium elements exceeds 11.2 mol / t, the effect as crystal nuclei is large, and not only Tc is lowered too much, but also metal elements contained in the polyethylene terephthalate film in a humid heat atmosphere. The hydrolysis reaction using the catalyst becomes dominant, and the heat-and-moisture resistance decreases.

  On the other hand, since manganese and calcium elements exist in an ionic state in the polyethylene terephthalate film, the charge of the entire film is brought close to 0, so that it interacts with ions of manganese and calcium elements and becomes an anion in the polyethylene terephthalate film. It is preferable to add a compound. In the present invention, phosphoric acid is preferably used as the compound that becomes an anion in the polyethylene terephthalate film from the viewpoint of heat and moisture resistance and heat resistance.

  The negative charge of phosphoric acid present as an anion in the polyethylene terephthalate film interacts with the positive charge of the cation of manganese and calcium elements, thereby canceling the positive charge of these cations. If all charges are eliminated, the effect of manganese and calcium element as a crystal nucleating agent cannot be obtained. Therefore, it is preferable to control the content and content ratio of manganese, calcium element and phosphoric acid. In order to obtain an effect as a crystal nucleating agent for manganese and calcium elements, the content of alkali metal element with respect to polyethylene terephthalate constituting the film is M1 (mol / t), and the content of manganese element with respect to polyethylene terephthalate constituting the film ( mol / t) and calcium element content (mol / t) are M2 (mol / t), and the phosphorus element content relative to polyethylene terephthalate constituting the film is P (mol / t). It is preferable that the metal content M (mol / t) in the polyethylene terephthalate obtained by the formula (iii) and the phosphorus element content P (mol / t) satisfy the following formula (iv).

(Iii) M = (M1) / 2 + M2
(Iv) 1.1 ≦ M / P ≦ 2.0
M in this formula represents the cation content of the metal element that interacts with the anion derived from phosphoric acid in the polyethylene terephthalate film. It is necessary to consider not only manganese and calcium but also a cation of an alkali metal element having a large electronegativity as a cation of a metal element that interacts with an anion derived from phosphoric acid.
However, since the anion derived from phosphoric acid in the polyethylene terephthalate film is divalent, it interacts with the cation of the divalent metal element in a 1: 1 ratio. Therefore, it is necessary to multiply the content M1 of the metal element that becomes a monovalent cation in the polyethylene terephthalate film by a coefficient of 0.5.

  By setting M / P within the above numerical range, the thermal characteristics of the film can be improved.

  The polyethylene terephthalate constituting the polyethylene terephthalate film of the present invention may contain an alkali metal element (particularly, a sodium element and / or a potassium element) in addition to manganese and calcium elements as metal elements. When the polyethylene terephthalate film of the present invention contains an alkali metal salt of phosphoric acid (particularly, a salt of phosphoric acid and sodium, and / or a salt of phosphoric acid and potassium), the heat and humidity resistance can be further improved. Because. However, when the alkali metal element is contained in the polyethylene terephthalate film, the formula (iv) is preferably satisfied.

  Moreover, the polyethylene terephthalate which comprises the film of this invention may contain metal elements other than the above in the range which does not impair the effect of this invention. For example, since antimony, titanium, germanium elements and the like are useful as a polymerization catalyst for polyethylene terephthalate, the polyethylene terephthalate film of the present invention may contain antimony elements, titanium elements, and germanium elements.

  The intrinsic viscosity of the polyethylene terephthalate constituting the film of the present invention is preferably 0.6 dl / g or more and 1.0 dl / g or less from the viewpoint of mechanical properties, heat resistance, and moist heat resistance. More preferably, it is 0.65 dl / g or more and 0.80 dl / g or less.

  The polyethylene terephthalate constituting the film of the present invention preferably has a terminal carboxyl group content of 1 equivalent / t or more and 25 equivalent / t or less from the viewpoint of moisture and heat resistance. More preferably, it is 18 equivalent / t or less, More preferably, it is 15 equivalent / t or less.

  The polyethylene terephthalate film of the present invention is a heat-resistant stabilizer, an oxidation-resistant stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, an organic / inorganic lubricant, organic, as long as the effects of the present invention are not impaired as necessary. Additives such as system / inorganic particles, fillers, nucleating agents, dispersing agents, coupling agents, etc. may be blended.

  The thickness of the film of the present invention is not particularly limited, but is preferably 20 μm or more and 350 μm or less. If the film thickness is less than 20 μm, the flatness of the film may deteriorate in the heat treatment step. When the film thickness exceeds 350 μm, the stretchability is poor, and the film forming property and flatness are deteriorated.

  In particular, when used as an insulating material for a compressor motor of an air conditioner, the polyester film is preferably thicker from the viewpoint of heat resistance, and is preferably 120 μm or more. When the polyester is in the shape of a film, decomposition of the polyester at a high temperature proceeds from the film surface. Therefore, by setting the thickness of the entire film to 120 μm or more, the amount of polyester decomposed at high temperatures is less than the total amount of polyester constituting the film, and the deterioration of the entire film is suppressed, improving the heat resistance. To do.

  Next, although an example is demonstrated about the manufacturing method of the polyethylene terephthalate film of this invention, this invention is limited to only the film obtained by this example, and is not interpreted.

  The polyester composition used as the raw material of the polyethylene terephthalate film of the present invention includes the following steps (9) to (10) in this order, in order to more efficiently express the effects of the present invention, It is preferable from the viewpoint of efficiently obtaining a polyethylene terephthalate film.

  (9) A step of dissolving the bishydroxyethyl terephthalate in the reaction vessel and then adding terephthalic acid and ethylene glycol to the melt to advance the esterification reaction.

  (10) A step of adding a polymerization catalyst to the esterification reaction product obtained in the step of (9) to advance the polymerization reaction to obtain a polyester composition.

  Addition of an ethylene glycol solution of germanium dioxide, antimony trioxide, titanium alkoxide, titanium chelate compound and the like is also suitably performed as a polymerization catalyst in the step (10) in the present invention.

  In addition, when adding phosphoric acid, an alkali metal phosphate, a manganese element, and a calcium element, it is preferable to add between the processes of (9) and (10). As a method for adding phosphoric acid, alkali metal phosphate, manganese element, and calcium element, it is preferable from the viewpoint of resistance to heat and moisture that it is preliminarily dissolved in ethylene glycol and mixed. As the manganese element and calcium element, it is preferable to use acetates of these elements. The solvent used at this time is preferably ethylene glycol from the viewpoints of heat resistance and heat and humidity resistance. When a glycol component other than ethylene glycol is used as a solvent, it may be copolymerized and heat resistance may be reduced. In particular, it is preferable to adjust the pH of the liquid mixture at this time to an acidity of 2.0 or more and 6.0 or less from the viewpoint of suppressing foreign matter formation. More preferably, it is 4.0 or more and 6.0 or less. These phosphorus compounds are preferably added with a polymerization catalyst added at intervals of 5 minutes or more from the viewpoint of polymerization reactivity. The phosphorus compound may be added either after the polymerization catalyst or before the addition.

  In this step, when phosphoric acid and alkali metal phosphate are added, the addition amount thereof is 1.3 mol / t or more and 3.0 mol / t or less as an alkali metal element with respect to the polyester composition, and phosphoric acid is phosphoric acid. It is preferable from the point of moist heat resistance to add 0.4 times or more and 1.7 times or less by mole number with respect to the acid alkali metal salt.

  In the step (10), it is preferable to perform polymerization until the intrinsic viscosity of the polyester composition is 0.5 dl / g or more.

  In the present invention, from the viewpoint of increasing the intrinsic viscosity and reducing the amount of terminal carboxyl groups, in the step (10), after forming into chips at an intrinsic viscosity of 0.5 dl / g to 0.6 dl / g, solid phase polymerization It is preferable to carry out the reaction. The solid phase polymerization reaction in the present invention is preferably performed at a polymerization temperature of Tm-30 ° C. or lower, Tm-60 ° C. or higher, and a vacuum degree of 0.3 Torr or lower of the polyester composition.

  The polyethylene terephthalate film of the present invention has high moisture and heat resistance, taking advantage of its features, such as solar battery back sheets, water heater motor electrical insulation materials, capacitor materials, automotive materials, and building materials. It can be suitably used for applications in which resistance to moist heat and concealment are important. In these, it uses suitably as a film for solar cell backsheets.

[Characteristic evaluation method]
A. Intrinsic viscosity IV
A sample is dissolved in 100 ml of orthochlorophenol (solution concentration C = 1.2 g / dl), and the viscosity of the solution at 25 ° C. is measured using an Ostwald viscometer. Similarly, the viscosity of the solvent is measured. Using the obtained solution viscosity and solvent viscosity, [η] (dl / g) is calculated by the following equation (a), and the obtained value is used as the intrinsic viscosity (IV).
(A) ηsp / C = [η] + K [η] ² · C
(Where ηsp = (solution viscosity (dl / g) / solvent viscosity (dl / g)) − 1, K is a Huggins constant (assuming 0.343)).

B. Content of phosphorus element, manganese element and calcium element of polyethylene terephthalate constituting the film is measured using a fluorescent X-ray analyzer (model number: 3270) manufactured by Rigaku Corporation.

C. Content of alkali metal element of polyethylene terephthalate constituting the film is measured by atomic absorption spectrometry (manufactured by Tadate Corporation: polarization Zeeman atomic absorption photometer 180-80, frame: acetylene-air).

D. The amount of terminal carboxyl groups is measured by the method of Malice (document MJ Malice, F. Huizinga, Anal. Chim. Acta, 22 363 (1960)).

E. Melting point (Tm)
In accordance with JIS K7121 (1999), a differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. was used, and a disk session “SSC / 5200” was used for data analysis. Perform the measurement.

  5 mg of the sample is weighed in a sample pan, and the sample is heated from 25 ° C. to 300 ° C. at a heating rate of 30 ° C./min (1stRUN), held in that state for 5 minutes, and then rapidly cooled to 25 ° C. or lower. Immediately thereafter, the temperature is raised again from 25 ° C. to 300 ° C. at a rate of 30 ° C./min to obtain a 2ndRUN differential scanning calorimetry chart (vertical axis is thermal energy and horizontal axis is temperature). In the differential scanning calorimetry chart of 2ndRun, the temperature of the peak top at the crystal melting peak, which is the endothermic peak, is obtained, and this is defined as Tm (° C.). When two or more crystal melting peaks are observed, the temperature of the peak top having the lowest temperature is defined as Tm (° C.).

F. Glass transition temperature (Tg)
In accordance with JIS K7121 (1999), a differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. was used, and a disk session “SSC / 5200” was used for data analysis. Perform the measurement.

  5 mg of the sample is weighed in a sample pan, and the sample is heated from 25 ° C. to 300 ° C. at a heating rate of 3 ° C./min (1stRUN), held in that state for 5 minutes, and then rapidly cooled to 25 ° C. or lower. Immediately thereafter, the temperature was increased again from 25 ° C. to 300 ° C. at a rate of temperature increase of 30 ° C./minute, and a 2ndRUN differential scanning calorimetry chart (the vertical axis represents thermal energy and the horizontal axis represents temperature) Get. In the 2ndRUN differential scanning calorimetry chart, in the step change portion of the glass transition, a straight line that is equidistant from the extended straight line of each base line in the vertical axis direction and a curve of the step change portion of the glass transition are Find from the point of intersection. When two or more stepwise changes in glass transition are observed, the glass transition temperature is obtained for each, and the average of these temperatures is taken as the glass transition temperature (Tg) (° C.) of the sample.

G. Crystallization temperature (Tc), Tc peak width According to JIS K7121 (1999), a differential scanning calorimeter “Robot DSC-RDC220” manufactured by Seiko Denshi Kogyo Co., Ltd. was used, and a disk session “SSC / 5200” was used for data analysis. ”To measure as follows.

  5 mg of the sample is weighed in a sample pan, and the sample is heated from 25 ° C. to 300 ° C. at a heating rate of 30 ° C./min (1stRUN), held in that state for 5 minutes, and then rapidly cooled to 25 ° C. or lower. Immediately thereafter, the temperature is increased again from 25 ° C. to 300 ° C. at a rate of temperature increase of 30 ° C./min to obtain a 2ndRUN differential scanning calorimetry chart (vertical axis is thermal energy and horizontal axis is temperature). From the differential scanning calorimetry chart of 2ndRUN, the temperature is obtained as the peak top temperature of the crystallization peak, which is an exothermic peak at the time of temperature rise, and this is defined as the crystallization temperature (Tc) (° C.). When two or more crystallization peaks are observed, the crystallization temperature is obtained from the peak top temperature of each peak, and the average of these temperatures is taken as the crystallization temperature (Tc) (° C.) of the sample.

The width of the Tc peak is obtained as follows.
The intersection of the tangent line and the baseline drawn at the point where the absolute value of the gradient is maximum on the low temperature side curve of the crystallization peak is the extrapolation crystallization start temperature (Tic) (° C), and the high temperature side curve of the crystallization peak The intersection of the tangent and the base line drawn at the point where the absolute value of the gradient is maximum is taken as the extrapolation crystallization end temperature (Tec), and is obtained by the following equation (b). Baseline is F.R. The base line on the high temperature side of the step-like change part in the term is extended to the high temperature side to form a baseline. When there are multiple Tc peaks, the intersection of the tangent line and the base line drawn at the point where the absolute value of the gradient is the maximum on the low temperature side curve of the lowest temperature side peak is the extrapolation crystallization start temperature (Tic), and the most The intersection of the tangent line and the baseline drawn on the high temperature side curve of the high temperature side peak at the point where the absolute value of the gradient is maximum is defined as the extrapolation crystallization end temperature (Tec) (° C.).
(B) Tc peak width (° C.) = | Tec−Tic |
H. FT-IR spectral intensity of polyethylene terephthalate film Using a Frontier FTIR manufactured by Perkin Elmer Co., Ltd., using a UATR IR unit, the medium crystal as diamond / ZnSe (refractive index 2.4), attenuated total reflection (ATR) Spectral intensity is measured by the method, single reflection). The resolution of the spectroscope is 1 cm ⁻¹ and the number of spectrum integrations is 16 times. The spectral intensity is the absorbance (arb. Unit) at each wavelength. In order to set the spectral intensity to the center value of the film thickness, the film is polished with a microtome to half the total film thickness, and the polished surface is used for measurement.

I. Moisture and heat resistance of polyethylene terephthalate film The film is cut into a size of 1 cm x 20 cm so that the long side is parallel to the longitudinal direction and the width direction of the film, and the tension is 5 cm between the chucks based on ASTM-D882 (1997). The elongation at break when measured at a speed of 300 mm / min is measured. The number of samples is n = 5, and after measuring in the longitudinal direction and the width direction of the film, the average value thereof is obtained, and this is defined as the elongation at break E0 of the film.

Next, the film cut out in the same manner is treated with a pressure cooker manufactured by Tabai Espec Co., Ltd. under high-humidity heat conditions of a temperature of 125 ° C. and a relative humidity of 100% RH, and then the elongation at break is measured. In addition, it is set as n = 5 and it measures about each of the longitudinal direction of a film, and the width direction, and let the average value be the breaking elongation E1. Using the obtained breaking elongations E0 and E1, the elongation retention is calculated by the following equation (c). The treatment time is changed by one hour, and the treatment time at which the elongation retention is 50% or less is defined as the elongation half-life.
(C) Elongation retention (%) = E1 / E0 × 100
From the obtained elongation half-life, the heat-and-moisture resistance of the film was determined as follows.
When elongation half-life is 70 hours or more: A
When the elongation half-life is 60 hours or more and less than 70 hours: B
When the elongation half-life is 51 hours or more and less than 60 hours: C
When elongation half-life is less than 51 hours: D
A, B and C are good, and A is the best among them.

J. et al. The amount of DEG contained in the polyethylene terephthalate film After dissolving the film at 150 ° C. using monoethanolamine as a solvent, a 1,6-hexanediol / methanol mixed solution is added to the solution and cooled. The cooled solution is neutralized by adding terephthalic acid, and after centrifuging, the supernatant is used for quantification by a calibration curve method using gas chromatography (GC-14A, manufactured by Shimadzu Corporation).

K. A flat film of the film is randomly cut into a 10 cm square, and left on a flat SUS plate, and then only two sides facing each other among the four sides are fixed with tape. When the surface of the SUS plate is 0 ° and the normal to the SUS plate surface is 90 °, the film is observed from 0 °, and the distance d between the surface of the SUS plate and the point of the film that floats most from the SUS plate surface is taking measurement. If d is 5 mm or less, the film flatness is good. If it exceeds 5 mm, the film flatness is x.

L. Film-forming properties Films were formed under the conditions of Examples and Comparative Examples, and the number of film breaks was converted to the number of breaks per hour. Many things were evaluated as x.

M.M. Film Thickness Film thicknesses were measured at arbitrary five locations using a dial gauge according to JIS K7130 (1992) A-2 method with 10 films stacked. The average value was divided by 10 to obtain the film thickness.
N. Heat resistance of the film The film is cut into a size of 1 cm × 20 cm so that the long side is parallel to the longitudinal direction and the width direction of the film, respectively, and based on ASTM-D882 (1997), the chuck is 5 cm and the pulling speed is 300 mm. Measure the elongation at break when pulled at / min. The number of samples is n = 5, and after measuring in the longitudinal direction and the width direction of the film, the average value thereof is obtained, and this is defined as the breaking strength E′0 of the film.

Next, the film cut out in the same manner was subjected to a dry heat treatment under a high temperature condition of 180 ° C. in a gear oven manufactured by Tabai Espec Co., Ltd. installed in a room maintained at 23 ° C. and a relative humidity of 65%. Thereafter, the elongation at break is measured. In addition, measurement is made into n = 5, it measures about each of the longitudinal direction of a film, and the width direction, and let the average value be the breaking elongation E'1. Using the obtained breaking elongations E′0 and E′1, the elongation retention is calculated by the following equation (d). The treatment time is changed by one hour, and the treatment time at which the elongation retention is 50% or less is defined as the elongation half-life.
(B) Elongation retention (%) = E′1 / E′0 × 100
From the obtained elongation half-life, the heat resistance of the film was determined as follows.
When elongation half-life is 140 hours or more: A
When elongation half life is 120 hours or more and less than 140 hours: B
When the elongation half-life is 100 hours or more and less than 120 hours: C
When elongation half-life is less than 100 hours: D
A, B, and C are good, and A is the best among them.

  In the above evaluation method, when the longitudinal direction and the width direction of the film to be evaluated are not known, the direction having the maximum refractive index in the film is regarded as the longitudinal direction, and the direction perpendicular to the longitudinal direction is regarded as the width direction. In addition, the direction of the maximum refractive index in the film may be obtained by measuring the refractive index in all directions of the film with an Abbe refractometer, for example, by using a phase difference measuring device (birefringence measuring device) or the like. You may obtain | require by determining an axial direction.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not necessarily limited to these.

(Polyester composition 1)
Polyester composition 1 was produced by the following method.
[Esterification reaction step] An esterification reaction vessel was charged with 105 parts by weight of bishydroxyethyl terephthalate (equivalent to 100 parts by weight of polyethylene terephthalate) and dissolved at 255 ° C. After dissolution, 86 parts by weight of terephthalic acid and 37 parts by weight of ethylene glycol were supplied to the reaction vessel, and the esterification reaction was allowed to proceed at 255 ° C. to discharge water. The esterification reaction was completed when the reaction rate reached 95% based on the amount of water that flowed out.
[Polymerization step] 105 parts by weight of the esterification reaction product (100 parts by weight of polyethylene terephthalate) was transferred to a polymerization reaction vessel, and 0.03 part by weight of antimony trioxide was slurried in 1.6 parts by weight of ethylene glycol while maintaining the temperature at 235 ° C. The solution obtained by dissolving 0.02 parts by weight of phosphoric acid in 1.6 parts by weight of ethylene glycol was added to the esterification reaction product. Thereafter, the temperature inside the polymerization reaction vessel was gradually increased from 235 ° C. to 280 ° C. over 90 minutes, and the inside of the vessel was gradually reduced from normal pressure to 150 Pa to proceed the reaction. The reaction was terminated when the intrinsic viscosity reached 0.55 dl / g to obtain a polyester composition 1-0.
[Solid Phase Polymerization Step] The polyester composition 1-0 obtained in the previous step was placed under vacuum at 160 ° C. for 6 hours to dry and crystallize the polyester composition. Thereafter, this was placed under vacuum at 220 ° C. for 8 hours for solid phase polymerization to obtain a polyester composition 1. The polyester composition 1 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 2)
A polyester composition 2 was obtained in the same manner as the polyester composition 1 except that 1.5 parts by weight of DEG was added simultaneously with the mixture of antimony trioxide in ethylene glycol slurry. Polyester composition 2 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 3)
A mixture in which 0.03 part by weight of antimony trioxide was slurried in 1.6 part by weight of ethylene glycol and a solution in which 0.02 part by weight of phosphoric acid was dissolved in 1.6 part by weight of ethylene glycol were added to the esterification reaction product. Instead, a solution prepared by dissolving 0.28 parts by weight of manganese acetate in 8.0 parts by weight of ethylene glycol was added, and then 0.03 parts by weight of antimony trioxide was slurried in 1.6 parts by weight of ethylene glycol. A polyester composition 3 was obtained in the same manner as the polyester composition 1 except that a mixture and a solution obtained by dissolving 0.10 parts by weight of phosphoric acid in 1.6 parts by weight of ethylene glycol were added. The obtained polyester composition 3 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.

(Polyester composition 4)
A polyester composition 4 was obtained in the same manner as the polyester composition 1 except that 0.3 parts by weight of DEG was added simultaneously with the mixture of antimony trioxide in ethylene glycol slurry. Polyester composition 4 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 5)
Polyester composition 5 was obtained in the same manner as polyester composition 1 except that 0.6 parts by weight of DEG was added simultaneously with the mixture of antimony trioxide in ethylene glycol slurry. The obtained polyester composition 5 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.

(Polyester composition 6)
A polyester composition 6 was obtained in the same manner as the polyester composition 4 except for the following points.
In [Polymerization step], a solution prepared by dissolving 0.02 parts by weight of manganese acetate in 8.0 parts by weight of ethylene glycol was added to the esterification reaction product, and then 0.03 parts by weight of antimony trioxide was added to 1.6 ml of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part and 0.01 weight part of phosphoric acid in 1.6 weight part of ethylene glycol.
Polyester composition 6 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 7)
A polyester composition 7 was obtained in the same manner as the polyester composition 5 except for the following points.
In [Polymerization step], a solution prepared by dissolving 0.02 parts by weight of manganese acetate in 8.0 parts by weight of ethylene glycol was added to the esterification reaction product, and then 0.03 parts by weight of antimony trioxide was added to 1.6 ml of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part and 0.01 weight part of phosphoric acid in 1.6 weight part of ethylene glycol.
The obtained polyester composition 7 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.

(Polyester composition 8)
A polyester composition 8 was obtained in the same manner as the polyester composition 4 except for the following points.
In [Polymerization step], after adding a solution prepared by dissolving 0.05 parts by weight of manganese acetate in 8.0 parts by weight of ethylene glycol, 0.03 part by weight of antimony trioxide was added to 1.6 parts of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part and 0.02 weight part of phosphoric acid in 1.6 weight part of ethylene glycol.
Polyester composition 8 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 9)
A polyester composition 9 was obtained in the same manner as the polyester composition 8 except for the following points.
-The point which added 0.4 weight part of DEG to the esterification reaction material in [polymerization process].
The obtained polyester composition 9 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.

(Polyester composition 10)
[Transesterification step] In a transesterification vessel, 100 parts by weight of dimethyl terephthalate, 0.01 parts by weight of manganese acetate, and 0.03 parts by weight of antimony trioxide in an ethylene glycol 57.degree. 5 parts by mass was melted or dissolved. Subsequently, it heated up to 230 degreeC over 3 hours, stirring, and by making methanol distill, it was made to transesterify and the transesterification product was obtained.
[Polymerization step] The transesterification product obtained in the previous step was polymerized at 150 Pa or less to obtain a polyester composition 10-0. The polymerization temperature is as follows.
Polymerization temperature: Polymerization was started at 230 ° C., and the temperature was gradually raised to finally 285 ° C.
[Solid Phase Polymerization Step] The polyester composition 10-0 obtained in the previous step was placed under vacuum at 160 ° C. for 6 hours to dry and crystallize the polyester composition. Thereafter, this was placed under vacuum at 220 ° C. for 8 hours for solid phase polymerization to obtain a polyester composition 10. The obtained polyester composition 10 had an intrinsic viscosity of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalents / t.

(Polyester composition 11)
A polyester composition 11 was obtained in the same manner as the polyester composition 1 except that 1.8 parts by weight of DEG was added simultaneously with the mixture of the antimony trioxide in ethylene glycol slurry. Polyester composition 11 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 12)
A polyester composition 12 was obtained in the same manner as the polyester composition 4 except for the following points.
In [Polymerization step], a solution prepared by dissolving 0.02 parts by weight of manganese acetate in 8.0 parts by weight of ethylene glycol was added to the esterification reaction product, and then 0.03 parts by weight of antimony trioxide was added to 1.6 ml of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part, 0.01 weight part of phosphoric acid, and 0.01 weight part of sodium dihydrogen phosphate dihydrate in 1.6 weight part of ethylene glycol.

  The obtained polyester composition 12 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.

(Polyester composition 13)
A polyester composition 13 was obtained in the same manner as the polyester composition 4 except for the following points.
In [Polymerization step], after adding a solution prepared by dissolving 0.05 parts by weight of manganese acetate in 8.0 parts by weight of ethylene glycol, 0.03 part by weight of antimony trioxide was added to 1.6 parts of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part, 0.01 weight part of phosphoric acid, and 0.03 weight part of sodium dihydrogen phosphate dihydrate in 1.6 weight part of ethylene glycol.

  Polyester composition 13 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 14)
A polyester composition 14 was obtained in the same manner as the polyester composition 4 except for the following points.
In [Polymerization step], a solution prepared by dissolving 0.02 parts by weight of calcium acetate in 8.0 parts by weight of ethylene glycol was added to the esterification reaction product, and then 0.03 parts by weight of antimony trioxide was added to 1.6 g of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part and 0.01 weight part of phosphoric acid in 1.6 weight part of ethylene glycol.
Polyester composition 6 obtained had an IV of 0.80 dl / g and a terminal carboxyl group content of 10.0 equivalents / t.

(Polyester composition 15)
A polyester composition 15 was obtained in the same manner as the polyester composition 5 except for the following points.
In [Polymerization step], a solution prepared by dissolving 0.02 parts by weight of calcium acetate in 8.0 parts by weight of ethylene glycol was added to the esterification reaction product, and then 0.03 parts by weight of antimony trioxide was added to 1.6 g of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part and 0.01 weight part of phosphoric acid in 1.6 weight part of ethylene glycol.
The obtained polyester composition 7 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.

(Polyester composition 16)
A polyester composition 16 was obtained in the same manner as the polyester composition 4 except for the following points.
In [Polymerization step], a solution prepared by dissolving 0.05 parts by weight of calcium acetate in 8.0 parts by weight of ethylene glycol was added to the esterification reaction product, and then 0.03 parts by weight of antimony trioxide was added to 1.6 parts of ethylene glycol. The point which added the solution which melt | dissolved the mixture slurried in the weight part and 0.02 weight part of phosphoric acid in 1.6 weight part of ethylene glycol.
The obtained polyester composition 16 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.

(Polyester composition 17)
A polyester composition 17 was obtained in the same manner as the polyester composition 16 except for the following points.
-The point which added 0.4 weight part of DEG to the esterification reaction material in [polymerization process].
The obtained polyester composition 17 had an IV of 0.80 dl / g and a terminal carboxyl group amount of 10.0 equivalent / t.
(Polyester composition 18)
A polyester composition 18 was obtained in the same manner as in the polyester composition 1 except for the following points.
-In the [polymerization step], the reaction was stopped when the intrinsic viscosity reached 0.66 dl / g, and the [solid phase polymerization step] was omitted.
The obtained polyester composition 18 had an IV of 0.66 dl / g and a terminal carboxyl group amount of 13.0 equivalents / t.

(Polyester composition 19)
A polyester composition 18 was obtained in the same manner as in the polyester composition 3 except for the following points.
-In the [polymerization step], the reaction was stopped when the intrinsic viscosity reached 0.66 dl / g, and the [solid phase polymerization step] was omitted.
Polyester composition 19 obtained had an IV of 0.66 dl / g and a terminal carboxyl group content of 13.0 equivalents / t.

Example 1
Polyester composition 1 was vacuum dried at a temperature of 180 ° C. for 2 hours. Subsequently, it supplied to the extruder under nitrogen atmosphere.

  The polyester composition 1 was melted in an extruder, discharged from a T-die at an extrusion temperature of 280 ° C., rapidly cooled with a casting drum (20 ° C.), and formed into a sheet by an electrostatic application method. This sheet was stretched in the longitudinal direction of the film and in the width direction of the film under the stretching conditions and heat treatment conditions described in the table, and subjected to a first heat treatment to obtain a film roll. Furthermore, the film unwound from the obtained film roll is used as a second heat treatment step in an oven having an inlet and an outlet heated to 170 ° C., and at the oven outlet so that the tension applied to the film becomes 50 N / m. While being wound, a polyethylene terephthalate film having a thickness of 50 μm was obtained in such a manner that the heat treatment time in the oven was 70 seconds, and the shrinkage of the film was 2% in MD and 2% in TD.

  The obtained polyethylene terephthalate film was excellent in heat and humidity resistance, flatness, and heat resistance. The characteristics of the obtained film are shown in the table.

(Examples 2-27, Comparative Examples 1, 2, 6-23)
A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the polyester composition used and the film forming conditions were as shown in the table. The characteristics and the like of the obtained polyester film are shown in the table.

  The crystallization temperature (Tc) of polyethylene terephthalate constituting the film is 145 ° C. or higher and 160 ° C. or lower, the width of the crystallization temperature (Tc) peak is 10 ° C. or higher and 25 ° C. or lower, and R1 and R2 are represented by the formula (i) The film satisfying the formula (ii) was a film excellent in wet heat resistance, flatness, and heat resistance.

  On the other hand, the crystallization temperature (Tc) of polyethylene terephthalate constituting the film is 145 ° C. or higher and 160 ° C. or lower, the width of the crystallization temperature (Tc) peak is 10 ° C. or higher and 25 ° C. or lower, and R1 and R2 are represented by the formula (ii) The film not satisfying any of the formulas was a film inferior in heat and moisture resistance and heat resistance.

(Examples 28 to 30)
A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the polyester composition used and the film forming conditions were as shown in the table and the film thickness was 350 μm. The characteristics of the obtained polyester film are shown in the table. As in Examples 1 to 3, the crystallization temperature (Tc) of polyethylene terephthalate constituting the film is 145 ° C. or higher and 160 ° C. or lower, and the width of the crystallization temperature (Tc) peak is 10 ° C. or higher and 25 ° C. or lower. The film in which R1 and R2 satisfy the formula (i) and the formula (ii) is excellent in moisture and heat resistance, flatness, and heat resistance, and particularly excellent in heat resistance.

(Comparative Example 3)
In the same manner as in Example 1, after using polyester composition 10 as a raw material, adding 0.05 wt% of sodium stearate as a crystal nucleating agent with respect to the weight of polyester composition 10 and melt-kneading in an extruder. Stretching and heat treatment were performed to obtain a polyethylene terephthalate film. The properties of the obtained polyethylene terephthalate film are shown in the table. By adding the crystal nucleating agent, the crystallization temperature (Tc) was lowered, but the width of the Tc peak was large, and the obtained polyethylene terephthalate film was inferior in heat-and-moisture resistance.

(Comparative Example 4)
After using polyester composition 10 as a raw material and adding 0.2 wt% of sodium stearate as a crystal nucleating agent with respect to the weight of polyester composition 10 and melt-kneading in an extruder, a sheet is obtained in the same manner as in Example 1. Turned into. From the obtained sheet, a polyethylene terephthalate film was obtained in the same manner as in Example 1. The properties of the obtained polyethylene terephthalate film are shown in the table. By adding the crystal nucleating agent, the crystallization temperature (Tc) was lowered, but the width of the Tc peak was large, and the obtained polyethylene terephthalate film was inferior in heat-and-moisture resistance.

(Comparative Example 5)
Using polyester composition 10 as a raw material, adding 0.1 wt% of sodium stearate as a crystal nucleating agent with respect to the weight of polyester composition 10, melt-kneading in an extruder, and then performing sheeting in the same manner as in Example 1. Turned into. From the obtained sheet, a polyethylene terephthalate film was obtained in the same manner as in Example 1. The properties of the obtained polyethylene terephthalate film are shown in the table. By adding the crystal nucleating agent, the crystallization temperature (Tc) was lowered, but the width of the Tc peak was large, and the obtained polyethylene terephthalate film was inferior in heat-and-moisture resistance.

(Comparative Example 24)
A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the polyester composition to be used and the film forming conditions were as shown in the table, and the film thickness was 380 μm. The obtained film was neither good in film formability nor flatness, and could not be measured for heat and moisture resistance and heat resistance.

(Comparative Example 25)
A polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the polyester composition used and the film forming conditions were as shown in the table and the film thickness was 15 μm. The obtained film was neither good in film formability nor flatness, and could not be measured for heat and moisture resistance and heat resistance.

“-” In the table indicates that the physical properties could not be measured because the flatness and film-forming property of the film were not good.

  The polyester film of the present invention has high wet heat resistance and flatness, and by taking advantage of its features, an electrical insulation material for a solar battery back sheet, a water heater motor, a compressor motor for an air conditioner, a capacitor material, It can be suitably used for applications in which moisture and heat resistance and concealment are important, such as automotive materials and building materials. In these, it uses suitably as a film for back sheets for solar cells, and a film for compressor motors for air conditioners.

Claims (5)

A polyethylene terephthalate film satisfying (1) and (2).
(1) The crystallization temperature (Tc) of polyethylene terephthalate constituting the film is 145 ° C. or higher and 160 ° C. or lower, and the width of the crystallization temperature (Tc) peak is 10 ° C. or higher and 25 ° C. or lower.
(2) The ratio R1 of the spectral intensity r1 observed at 1388 cm ⁻¹ and the spectral intensity r2 observed at 1372 cm ⁻¹ when the polyethylene terephthalate film was measured by Fourier transform infrared spectroscopy (FT-IR). satisfied but the formula (i), and the spectral intensity r3 observed at 988cm ^-1, the ratio R2 of the spectral intensity r4 observed at 971cm ^-1 is (ii) satisfying the formula.
(I) 0.70 ≦ R1 ≦ 0.94
(Ii) 0.60 ≦ R2 ≦ 0.73
However, R1 = r1 / r2, R2 = r3 / r4 The polyethylene terephthalate film according to claim 1, wherein a content of diethylene glycol in the polyethylene terephthalate constituting the polyethylene terephthalate film is 0.7 wt% or more and 2.0 wt% or less. The polyethylene terephthalate film according to claim 1 or 2, satisfying (3) to (5).
(3) The polyethylene terephthalate constituting the film contains one or more metal elements of manganese and calcium, and the content thereof is 0.6 mol / t or more and 11.2 mol / t or less with respect to polyethylene terephthalate. .
(4) Polyethylene terephthalate constituting the film contains a phosphorus element. (5) M1 (mol / t) of alkali metal element content relative to polyethylene terephthalate constituting the film, manganese element content relative to polyethylene terephthalate constituting the film. When the total of the amount (mol / t) and the calcium element content (mol / t) is M2 (mol / t) and the content of phosphorus element with respect to polyethylene terephthalate constituting the film is P (mol / t), The metal content M (mol / t) in the polyethylene terephthalate obtained by the formula (iii) and the phosphorus element content P (mol / t) satisfy the following formula (iv).
(Iii) M = (M1) / 2 + M2
(Iv) 1.1 ≦ M / P ≦ 2.0 The intrinsic viscosity (IV) of polyethylene terephthalate constituting the film is 0.65 dl / g or more and 0.80 dl / g or less, and the amount of terminal carboxyl groups is 1 equivalent / t or more and 25 equivalent / t or less. A polyethylene terephthalate film according to claim 1. 5. The method for producing a polyethylene terephthalate film according to any one of claims 1 to 4, comprising the steps according to (6) to (8).
(6) A biaxial stretching process in which the film is biaxially stretched at an area magnification of 13.5 times or more in the longitudinal direction (MD) and the width direction (TD) of the film at a temperature T1n (° C.) satisfying the following formula (v). (V) Tg ≦ T1n ≦ Tg + 40
Tg: Glass transition temperature (° C.) of polyethylene terephthalate constituting the film
(7) After the step (6), a first heat treatment step (vi) Tm−90 ≦ Th1 ≦ Tm−45 in which heat treatment is performed at a heat treatment temperature Th1 (° C.) satisfying the following formula (vi).
Tm: melting point (° C.) of polyethylene terephthalate constituting the film
(8) After the step (7), at a heat treatment temperature Th2 (° C.) satisfying the following formula (vii), the film length direction (MD) and film width direction ( TD) Second heat treatment step (vii) Tc ≦ Th2 ≦ Th1 for shrinking both by 1% or more and 10% or less
Tc: Crystallization temperature of polyethylene terephthalate constituting the film (° C.)