Hydrolysis-resistant polyester film

Abstract

Provided is a hydrolysis-resistant polyester film having a low acid value due to suppression of acid value-increase during film formation. The hydrolysis-resistant polyester film of the present invention is a polyester film comprising a polyester resin composition, wherein the polyester resin composition that forms the films comprises 0.03 to 6.7 eq/ton of hindered phenol structural units, an acid value of a polyester that forms the film is less than 25 eq/ton, and an intrinsic viscosity of a polyester that forms the film is more than 0.64 dL/g and not less than 0.90 dL/g.

Claims

1. A hydrolysis-resistant polyester film comprising a polyester resin composition, wherein the polyester resin composition that forms the film contains 0.03 to 6.7 eq/ton of hindered phenol structural units, an acid value of a polyester that forms the film is less than 25 eq/ton, an intrinsic viscosity of a polyester that forms the film is more than 0.64 dL/g and not more than 0.90 dL/g, and the polyester is polymerized using a polymerization catalyst comprising an antimony compound in combination with a calcium compound, a lithium compound, and a phosphorus compound, the polyester resin comprises Sb atoms in an amount of from 70 ppm to 400 ppm, Ca atoms in an amount of from 50 ppm to 400 ppm, Li atoms are present in an amount of from 20 ppm to 300 ppm, and P atoms in an amount of from 100 ppm to 1,000 ppm, and the polyester resin composition does not substantially contain a compound having a substituent reactive with an OH group or a carboxyl group, except an OH group and a carboxyl group.

2. The hydrolysis-resistant polyester film according to claim 1, wherein the polyester comprises terephthalic acid and/or naphthalenedicarboxylic acid as acid components, the total content of the terephthalic acid and naphthalenedicarboxylic acid is not less than 90 mol % based on total acid components, the polyester comprises ethylene glycol and/or diethylene glycol as glycol components, and the total content of the ethylene glycol and diethylene glycol is not less than 90 mol % based on total glycol components.

3. The hydrolysis-resistant polyester film according to claim 1, wherein the polyester is homo-polyethylene terephthalate or homo-polyethylene naphthalate.

4. The hydrolysis-resistant polyester film according to claim 1, wherein the polyester is a copolymer having ethylene terephthalate as a main constituent, the content of acid components other than terephthalic acid is not more than 7 mol % based on total acid components, and/or the content of glycol components other than ethylene glycol is not more than 7 mol % based on total glycol components.

5. The hydrolysis-resistant polyester film according to claim 4, wherein in the polyester, the total content of acid components other than terephthalic acid and glycol components other than ethylene glycol, which form the polyester, is not more than 7 mol % based on the sum of total acid components and total glycol components.

6. The hydrolysis-resistant polyester film according to claim 1, wherein the polyester content in the polyester resin composition is more than 90% by mass.

7. The hydrolysis-resistant polyester film according to claim 1, wherein the thermal-oxidative decomposition resistance parameter (TOD) of the polyester resin composition that forms the film is not more than 0.25.

8. The hydrolysis-resistant polyester film according to claim 1, wherein the apparent specific gravity of the film is 0.7 to 1.3.

9. The hydrolysis-resistant polyester film according to claim 1, wherein the polyester resin composition contains a hindered phenol compound in an amount of not less than 10 ppm and less than 200 ppm.

10. The hydrolysis-resistant polyester film according to claim 1, wherein the hindered phenol compound is added to the polyester resin composition during film formation.

11. The hydrolysis-resistant polyester film according to claim 1, wherein the hydrolysis-resistant polyester film is for use in a solar cell back sheet, a solar cell front sheet or electrical insulation.

12. A solar cell, wherein the polyester film according to claim 1 is laminated on at least any one of a light receiving surface and a surface opposite to the light receiving surface.

13. A method of preparing the hydrolysis-resistant polyester film according to claim 1, comprising melting in an extruder polyester chips polymerized using a polymerization catalyst, wherein the polymerization catalyst comprises an antimony compound in combination with a calcium compound, a lithium compound, and a phosphorus compound; forming a non-drawn film by extruding the molten resin from the extruder; drawing the non-drawn film in at least one direction; and heating the drawn film to obtain the polyester film.

14. The method according to claim 13, wherein the moisture content of the resin composition is not more than 100 ppm.

15. The hydrolysis-resistant polyester film according to claim 1, wherein the polyester resin composition contains less than 0.1% by mass of a compound having a substituent reactive with an OH group or a carboxyl group, except an OH group and a carboxyl group.

16. The hydrolysis-resistant polyester film according to claim 15, wherein the polyester resin composition contains less than 0.01% by mass of a compound having a substituent reactive with an OH group or a carboxyl group, except an OH group and a carboxyl group.

Description

EXAMPLES

(1) The present invention will be described more specifically below by way of Examples, but the present invention is not limited by Examples described below, and can be implemented while being appropriately modified within the bounds of not departing from the aforementioned and below-mentioned teachings, and these modifications are all encompassed within the technical scope of the present invention.

(2) (1) Content of Hindered Phenol Structure in Film Composition

(3) In Examples, the content was calculated from the amount of a hindered phenol added during polymerization or as a master batch.

(4) For example, when Irganox (registered trademark) 1330 was added at the start of polycondensation in an amount of 200 ppm based on the mass of a resin after polymerization, the content thereof is as follows: 200/775.2 (molecular weight of Irganox (registered trademark) 1330)3 (number of hindered phenol structures per molecule of Irganox (registered trademark) 1330)=0.77.

(5) (2) Intrinsic Viscosity (IV) of Polyester

(6) A sample was crushed, dried, and then dissolved in a mixed solvent of phenol/1,1,2,2-tetrachloroethane (6/4 (mass ratio)). The solution was subjected to a centrifugal separation treatment to remove inorganic particles and unnecessary substances (void forming agent in the case of a void-containing film), followed by making a measurement at 30 C. using an Ubbelohde viscometer. Calculation was performed with the mass of only a polyester by subtracting the mass of components other than the polyester from the mass of the sample.

(7) (3) Content of Diethylene Glycol (DEG Content)

(8) The polyester (0.1 g) was decomposed by heating in 2 ml of methanol at 250 C., followed by performing quantification by gas chromatography to determine a DEG content.

(9) (4) Method for Measurement of Acid Value

(10) A. Preparation of Sample

(11) A sample was crushed, dried under vacuum at 70 C. for 24 hours, and then weighed to 0.200.0005 g using a balance. The mass at this time was designated as W (g). Benzyl alcohol (10 ml) and the weighed sample were added in a test tube, the test tube was immersed in a benzyl alcohol bath heated to 205 C., and the sample was dissolved with stirring by a glass rod. Samples with the dissolution time of 3 minutes, 5 minutes and 7 minutes were designated as A, B and C, respectively. Then, a test tube was newly provided, only benzyl alcohol was added therein, a treatment was carried out in the same procedure as described above, and samples with the dissolution time of 3 minutes, 5 minutes and 7 minutes were designated as a, b and c, respectively.

(12) B. Titration

(13) Titration was performed using 0.04 mol/l of an aqueous potassium hydroxide solution (ethanol solution), the factor of which is known in advance. A titer (ml) of the aqueous potassium hydroxide solution was determined by using phenol red as an indicator and considering as an end point a point at which the color of the solution was changed from yellowish green to pink. The titers of samples A, B and C are designated as XA, XB and XC (ml), respectively. The titers of samples a, b and c are designated as Xa, Xb and Xc (ml), respectively.

(14) C. Calculation of Acid Value

(15) Using titers XA, XB and XC for the respective dissolution times, a titer V (ml) at a dissolution time of 0 minute was determined by a least square method. Similarly, a titer V0 (ml) was determined using Xa, Xb and Xc. Then, a carboxyl terminal concentration was determined in accordance with the following equation.
Acid value(eq/ton)=[(VV0)0.04NF1000]/W
NF: factor of 0.04 mol/l of aqueous potassium hydroxide solution
W: sample mass (g)

(16) When components other than the polyester as in the case of a void-containing film are included, W is a mass of only the polyester which is obtained by subtracting the mass of components other than the polyester from the total mass.

(17) (5) Content of Cyclic Trimer (Hereinafter Referred to as CT Content)

(18) A sample was dissolved in a mixed liquid of hexafluoroisopropanol/chloroform, and diluted by further adding chloroform. Methanol is added thereto to precipitate a polymer, followed by carrying out filtration. The filtrate was evaporated to dryness, the volume was made constant with dimethylformamide, and a cyclic trimer formed of ethylene terephthalate units was quantified by a liquid chromatography method.

(19) (6) Content of Acetaldehyde (Hereinafter Referred to as AA Content)

(20) Sample/distilled water (=1 gram/2 ml) was placed in a glass ampule replaced with nitrogen, the top of the ampule was sealed, an extraction treatment was carried out at 160 C. for 2 hours, acetaldehyde in the extract was measured by high-sensitive gas chromatography after cooling, and the concentration was expressed in ppm.

(21) The AA contents of films of Examples and Comparative Examples were in a range of 15 to 23 ppm.

(22) (7) Thermal-Oxidative Decomposition Parameter (TOD)

(23) A film ([IV]i) was frozen and crushed into a powder of not more than 20 mesh. The powder was dried under vacuum at 130 C. for 12 hours, and 300 mg of the powder was placed in a glass test tube having an inner diameter of about 8 mm and a length of about 140 mm, and dried under vacuum at 70 C. for 12 hours. Then, the test tube was immersed in a salt bath at 230 C. under air dried by attaching to the top of the test tube a drying tube containing silica gel, and heated for 15 minutes, and thereafter [IV]f1 was measured.

(24) The TOD was determined in the following manner. It is to be noted that [IV]i and [IV]f1 represent IV (dL/g) before and after the heating test, respectively. Freezing and crushing were carried out using a freezer mill (Model 6750 manufactured by SPEX CentriPrep in U.S.A.). About 2 g of resin chips or a film and a special impactor were placed in a special cell, the cell was thereafter set in a device, the device was filled with liquid nitrogen, and retained for about 10 minutes, and the crushing was then carried out for 5 minutes at RATE 10 (the impactor is reciprocated about 20 times per second).
TOD=0.245{[IV]f1.sup.(1.47)[IV]i.sup.(1.47)}
(8) Moisture Content of Polyester Chips

(25) Chips (1 to 2 g) were heat-treated under conditions of 230 C. and 10 minutes to volatilize moisture contained in chips, and the moisture content was measured using a moisture content measuring device (Model VA-05 manufactured by Mitsubishi Kasei Corporation).

(26) (9) Evaluation of Hydrolysis Resistance (Fracture Elongation Retention)

(27) As evaluation of hydrolysis resistance, a HAST (Highly Accelerated temperature and humidity Stress Test) standardized in JIS C-60068-2-66 was conducted. The test was conducted under conditions of 105 C., 100% RH and 0.03 MPa using EHS-221 manufactured by ESPEC CORP for the instrument.

(28) A film was cut into 70 mm190 mm, and the film was placed using a jig. The films were placed while keeping such a distance that they did not contact one another. A treatment was carried out under conditions of 105 C., 100% RH and 0.03 MPa for 200 hours and 300 hours. Fracture elongations before and after the treatment were measured in accordance with JIS C-2318-1997 5.3.31 (tensile strength and elongation), and a fracture elongation retention was calculated in accordance with the following equation.
Fracture elongation retention(%)=[(fracture elongation(%) after treatment)/(fracture elongation(%) before treatment)]100
(10) Fracture Elongation Retention Half Life of Heat Resistance Test at 160 C.

(29) A film was cut out in a longer direction into a strip sample having a length of 200 mm and a width of 10 mm, and used. A fracture elongation was measured at 25 C. and 65% RH using a tensile test device in accordance with a method specified in JISK-7127. The initial tensile chuck-to-chuck distance was 100 mm, and the tensile speed was 300 m/minute. Measurements were made 20 times with the sample changed from one to another, and an average value (X) of fracture elongations thereof was determined. A strip sample having a length of 200 mm and a width of 10 mm was placed in a gear oven, left standing under an atmosphere at 160 C., and then naturally cooled, and for this sample, a tensile test was conducted 20 times under the same conditions as described above, and an average value (Y) of fracture elongations thereof was determined. A fracture elongation retention was determined by the following equation from the average values (X) and (Y) of fracture elongations obtained.
Fracture elongation retention(%)=(Y/X)100

(30) The heat treatment time taken until the fracture elongation retention was not more than 50% was determined, and designated as a fracture elongation retention half life.

(31) (11) Content (ppm) of Metal Element and Content (ppm) of Phosphorus Element

(32) A sample was incinerated/acid-dissolved, followed by determining the content by high-frequency plasma emission spectrometry or atomic absorption spectroscopy.

(33) (12) Apparent Specific Gravity

(34) A film was accurately cut out into a square of 10 cm10 cm, the thickness thereof was measured at 50 points, and an average thickness t (unit: m) was determined. Next, the mass of the sample was measured to 0.1 mg, and the measured value was designated as w (unit: g). Then, the apparent specific gravity was calculated by the following equation.
Apparent specific gravity()=(w/t)10000
(13) Whiteness Degree

(35) A measurement was made using Z-1001DP manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD. in accordance with the JIS-L1015-1981-B method for the whiteness degree.

(36) (14) Contamination of Die Lip, Roll and the Like

(37) Degrees of contamination of the periphery of a die lip, a cooling roll, a conveyance roll at each position and a drawing roll after film formation were visually observed, and evaluations were made in three grades of A, B and C.

(38) A: Comparable to a polyester containing no hindered phenol.

(39) B: There is a slight increase in deposits on the periphery of a lip, or a part of the roll is slightly clouded.

(40) C: Operability may be deteriorated because there is an apparent increase in deposits on the periphery of a lip, a roll is clouded, or the like.

(41) (15) Content of Acid Components Other than Terephthalic Acid Component and Glycol Components Other than Ethylene Glycol Component

(42) A measurement was made by adjusting the composition of a copolymerization monomer so as to have a predetermined copolymerization ratio during polymerization. The obtained polyester was dissolved in a mixed solvent of heavy chloroform:trifluoroacetic acid=9:1 (volume ratio), and a measurement was made by .sup.1H-NMR (NMR, AVANCE 500 manufactured by BRUKER Corporation) to confirm that predetermined amounts of components were copolymerized.

(43) (16) Thermal Shrinkage Coefficient of Film at 150 C. (HS150)

(44) A film was cut into a size of 10 mm in width and 250 mm in length along such a direction that longer sides (250 mm) each coincided with the longer direction and the width direction, the film was marked at an interval of 200 mm, and an interval A was measured under a fixed tension of 5 g. Subsequently, the film was left standing in an oven in an atmosphere of 150 C. for 30 minutes under no-load. The film was taken out from the oven and cooled to room temperature, a marked interval B was determined under a fixed tension of 5 g, and a thermal shrinkage coefficient was determined by the following equation.

(45) The thermal shrinkage coefficient of the film at 150 C. was measured at intervals of 100 mm in the film width direction, average values for 3 samples were rounded off to two decimal places, and a value in one of the longer direction and the width direction, which had a greater value, was used.
Thermal shrinkage coefficient(%)=[(AB)/A]100

Examples 1 to 3

(46) Magnesium acetate tetrahydrate was added into a mixture of terephthalic acid and ethylene glycol so that the concentration in a polyester was 120 ppm in terms of a Mg atom, and the mixture was reacted at a temperature of 255 C. at normal pressure. Thereafter, thereto were further added antimony trioxide in such an amount that the concentration in the polyester was 250 ppm in terms of an Sb atom, cobalt acetate tetrahydrate in such an amount that the concentration in the polyester was 30 ppm in terms of a Co atom and trimethyl phosphate in an such an amount that the concentration in the polyester was 150 ppm in terms of a P atom, and the mixture was further reacted at a temperature of 260 C.

(47) Subsequently, the reaction product was transferred to a polycondensation reaction tank, and a hindered phenol compound (Irganox 1330) in an amount shown in Table 1 and silica particles having an average particle diameter of 1.0 m were added so that the concentration in the polyester was 800 ppm. Then, the reaction system was gradually decompressed while elevating the temperature by heating, and polymerized at 290 C. under a reduced pressure of 133 Pa (1 mmHg) using conventional methods, to obtain chips having an IV of 0.60 dL/g. Subsequently, using a rotation-type vacuum polymerization apparatus, solid phase polycondensation was conducted at 220 C. under a reduced pressure of 67 Pa (0.5 mmHg) to obtain a resin composition having an intrinsic viscosity of 0.76 dL/g and an acid value of 5 eq/ton. The content of a cyclic trimer (CT) was 0.29% by mass.

(48) Chips of the polyester resin composition obtained was dried to a moisture content of 17 ppm, fed into an extruder, and extruded in a sheet form from a die while the resin maximum temperature in an extruder melting part, a kneading part, a polymer tube, a gear pump and a filter was set at 290 C. and the resin maximum temperature in subsequent polymer tubes was set at 285 C. These polymers were each filtered using a filter medium of a stainless sintered body (nominal filtration accuracy: 20 m particle 95% cut). A flat die was set so that the resin temperature was 285 C. The extruded resin was wound around a casting drum having a surface temperature of 30 C., and solidified by cooling to prepare a non-drawn film.

(49) Next, the non-drawn film was heated to 100 C. with a group of heated rolls and an infrared heater, and thereafter drawn at a ratio of 3.3 in a longer direction by a group of rolls having a difference in circumferential speed, so that a uniaxially oriented PET film was obtained. Subsequently, the uniaxially oriented PET film was drawn at a ratio of 4.0 in a width direction at 130 C. in a tenter, heat-set at 235 C., and further subjected to a relaxation treatment at 200 C. in the width direction to obtain a biaxially oriented PET film having a thickness of 50 m.

(50) The results are shown in Table 1.

(51) TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Hindered phenol compound IRG1330 IRG1330 IRG1330 Content of Hindered phenol 30 100 200 compound (ppm) Content of Hindered phenol 0.12 0.39 0.77 structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 glycol) IV of film (dL/g) 0.71 0.73 0.73 IV of raw material PET 0.76 0.76 0.76 (dL/g) AV of film (eq/ton) 9 8 8 AV of raw material PET 5 5 5 (eq/ton) Content of CT in film (% by 0.4 0.4 0.4 mass) Kind of Catalyst Sb Sb Sb TOD 0.25 0.04 0.01 Result of HAST test (105 C., 70 88 92 300 hr, %) Fracture elongation 800 1000 1000 retention half life at 160 C. (hr) Contamination of die lip, A A A roll and the like IRG1330: Irganox 1330, manufactured by BASF Japan Ltd.

Examples 4 to 10 and Comparative Examples 1 to 2

(52) Chips of the polyester resin composition obtained by solid phase polymerization having an IV of 0.76 dL/g and an acid value of eq/ton was obtained in the same manner as in Example 1, except that a hindered phenol compound was not added. The Chips was dried to a moisture content of 15 ppm, dried chips and a hindered phenol compound were fed into a biaxial extruder, and melted and kneaded under reduction of pressure with a vent to obtain a master batch containing a hindered phenol compound of 50000 ppm.

(53) The obtained chips of a solid phase polymerized polyester and a master batch containing a hindered phenol compound were dried to a moisture content of 17 ppm, and film formation was carried out in the same manner as in Example 1, to prepare a film. The results are shown in Table 2.

(54) From the results of Examples 4 to 10 and Comparative Examples 1 and 2, it was found that deterioration of film during film formation was suppressed by increase of hindered phenol structures and weather resistance was improved. In addition, in Comparative Example 2, there were a few of attached substances on die lip parts and chill roll parts.

Comparative Example 3

(55) Polycondensation reaction was carried out in the same manner as in Examples 1 to 3, except that a hindered phenol compound was not added during polycondensation and the time of solid phase polymerization was lengthened, to obtain chips of a solid phase polymerized polyester resin composition. In addition, PET film was produced in the same manner as in Example 1 and the temperature was controlled such that the pressure of a polyester resin in each of film formation steps was comparable to that of Example 3. Specifically, the resin maximum temperature in an extruder melting part, a kneading part, a polymer tube, a gear pump and a filter was set at 300 C. and the resin maximum temperature in subsequent polymer tubes was set at 290 C.

(56) The results are shown in Table 2. Although the intrinsic viscosity of film was the same as those of Examples, the high temperature was required in film formation step since it was necessary to increase the intrinsic viscosity of a raw material polyester. As a result, decomposition was processed, and the acid value of the film was increased, leading to poor weather resistance.

(57) TABLE-US-00002 TABLE 2 Com- Com- Example parative Comparative parative Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 10 Example 1 Example 2 Example 3 Hindered phenol compound IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 Content of Hindered 15 30 60 200 400 700 1200 5 2200 0 phenol compound (ppm) Content of Hindered 0.06 0.12 0.23 0.77 1.55 2.71 4.6 0.02 8.51 0 phenol structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 glycol) IV of film (dL/g) 0.71 0.72 0.73 0.73 0.73 0.73 0.73 0.69 0.73 0.73 IV of raw material PET 0.76 0.76 0.76 0.76 0.76 0.76 0.76 0.76 0.76 0.81 (dL/g) AV of film (eq/ton) 9 8 8 8 8 8 8 12 9 16 AV of raw material PET 5 5 5 5 5 5 5 5 5 4 (eq/ton) Content of CT in film (% 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 by mass) Kind of Catalyst Sb Sb Sb Sb Sb Sb Sb Sb Sb Sb TOD 0.23 0.1 0.01 0.01 0.01 0.01 0.01 0.3 0.01 0.38 Result of HAST test 70 85 90 93 91 93 93 60 90 60 (105 C., 300 hr, %) Fracture elongation 750 900 1000 1200 1100 1200 1300 600 1000 600 retention half life at 160 C. (hr) Contamination of die lip, A A A A A A A to B A B A roll and the like IRG1330: Irganox 1330, manufactured by BASF Japan Ltd.

Examples 11 and 12

(58) Examples 11 and 12 were carried out in the same manner as in Example 1 except that the added hindered phenol compound and the added amount were changed. The results are shown in Table 3.

Example 13

(59) A polyester having an IV of 0.55 dL/g was produced by melt polymerization and was solid phase polymerized to obtain chips of a solid phase polymerized polyester resin composition having an IV of 0.68 dL/g and an acid value of 6 eq/ton. The others were carried out in the same manner as in Example 3.

(60) PET film was produced in the same manner as in Example 3, but the temperature was controlled such that the pressure of a polyester resin in each of film formation steps was comparable to that of Example 3. Specifically, the resin maximum temperature in an extruder melting part, a kneading part, a polymer tube, a gear pump and a filter was set at 288 C. and the resin maximum temperature in subsequent polymer tubes was set at 285 C. The results were good level, but weather resistance was inferior to that of Example 3 due to low molecular weight. The results are shown in Table 3.

Example 14

(61) Polycondensation reaction was carried out in the same manner as in Example 3 except that the time of solid phase polymerization was lengthened, to obtain chips of a solid phase polymerized polyester resin composition. In addition, PET film was produced in the same manner as in Example 3 and the temperature was controlled such that the pressure of a polyester resin in each of film formation steps was comparable to that of Example 3. Specifically, the resin maximum temperature in an extruder melting part, a kneading part, a polymer tube, a gear pump and a filter was set at 305 C. and the resin maximum temperature in subsequent polymer tubes was set at 290 C. Although the acid value was slightly high, weather resistance was excellent since molecular weight was maintained. The results are shown in Table 3.

Comparative Example 4

(62) A polyester having an IV of 0.68 dL/g was produced by melt polymerization and was solid phase polymerized to obtain chips of a solid phase polymerized polyester resin composition having an IV of 0.76 dL/g and an acid value of 23 eq/ton. The others were carried out in the same manner as in Example 3.

(63) The results are shown in Table 3. Although hindered phenol structures were contained, the acid value was high and weather resistance was poor.

Comparative Example 5

(64) A polyester having an IV of 0.52 dL/g was produced by melt polymerization and was solid phase polymerized to obtain chips of a solid phase polymerized polyester resin composition having an IV of 0.64 dL/g and an acid value of 5 eq/ton. The others were carried out in the same manner as in Example 3.

(65) The results are shown in Table 3. Although hindered phenol structures were contained, the intrinsic viscosity was low and weather resistance was poor.

(66) TABLE-US-00003 TABLE 3 Comparative Comparative Example 11 Example 12 Example 13 Example 14 Example 4 Example 5 Hindered phenol compound IRG1098 IRG1098 IRG1330 IRG1330 IRG1330 IRG1330 Content of Hindered 100 200 200 200 200 200 phenol compound (ppm) Content of Hindered 0.31 0.63 0.77 0.77 0.77 0.77 phenol structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 1.2 1.2 1.2 glycol) IV of film (dL/g) 0.73 0.73 0.67 0.8 0.73 0.62 IV of raw material PET 0.76 0.76 0.68 0.85 0.76 0.64 (dL/g) AV of film (eq/ton) 8 8 8 11 27 7 AV of raw material PET 5 5 6 4 23 5 (eq/ton) Content of CT in film (% 0.4 0.4 0.4 0.35 0.9 0.4 by mass) Kind of Catalyst Sb Sb Sb Sb Sb Sb TOD 0.04 0.01 0.01 0.01 0.01 0.01 Result of HAST test 91 94 86 88 20 50 (105 C., 300 hr, %) Fracture elongation 1000 1100 1000 1100 800 600 retention half life at 160 C. (hr) Contamination of die A A A A A A lip, roll and the like IRG1098: Irganox 1098, manufactured by BASF Japan Ltd. IRG1330: Irganox 1330, manufactured by BASF Japan Ltd.

Examples 15 to 18

(67) Examples 15 to 18 were carried out in the same manner as in Example 4 except that a master batch was produced from a hindered phenol compound shown in Table 4 and the added amount of a hindered phenol compound was changed during film formation. The similar effects were found in the case where the hindered phenol compound was changed.

(68) TABLE-US-00004 TABLE 4 Exam- Exam- Exam- Exam- ple 15 ple 16 ple 17 ple 18 Hindered phenol IRG1222 IRG1222 IRG1010 IRG1010 compound Content of Hindered 100 200 100 200 phenol compound (ppm) Content of Hindered 0.28 0.56 0.34 0.68 phenol structure (eq/ton) Content of DEG (mol 1.2 1.2 1.2 1.2 % in glycol) IV of film (dL/g) 0.73 0.73 0.73 0.73 IV of raw material PET 0.76 0.76 0.76 0.76 (dL/g) AV of film (eq/ton) 8 8 8 8 AV of raw material PET 5 5 5 5 (eq/ton) Content of CT in film (% 0.4 0.4 0.4 0.4 by mass) Kind of Catalyst Sb Sb Sb Sb TOD 0.01 0.01 0.01 0.01 Result of HAST test 92 92 92 90 (105 C., 300 hr, %) Fracture elongation 1000 1000 1000 1100 retention half life at 160 C. (hr) Contamination of die lip, A A A A roll and the like IRG1222: Irganox 1222, manufactured by BASF Japan Ltd. IRG1010: Irganox 1010, manufactured by BASF Japan Ltd.

Example 19 and Comparative Example 6

(69) A solution of calcium acetate and ethylene glycol was added to a mixture of dimethyl terephthalic acid and ethylene glycol such that the remaining concentration of calcium element was 200 ppm, and the mixture was subjected to ester exchange reaction according to usual methods, to obtain an oligomer mixture. Trimethyl phosphate was added to the oligomer mixture such that the remaining concentration of phosphorus element was 350 ppm, and stirred at 200 C. for 10 minutes in normal pressure under nitrogen atmosphere. Thereafter, the mixture of antimony trioxide and ethylene glycol solution and lithium acetate and ethylene glycol solution was added thereto such that the remaining concentration of antimony element was 200 ppm and the remaining concentration of lithium element was 100 ppm. The mixture was further stirred at 250 C. for 10 minutes in normal pressure under nitrogen atmosphere. Then, the temperature was elevated to 280 C. for 60 minutes while the reaction system was gradually decompressed to be 13.3 Pa (0.1 Torr), and polycondensed at 280 C. under a reduced pressure of 13.3 Pa, to obtain chips made of a polyester having an IV of 0.58 dL/g.

(70) Subsequently, using a rotation-type vacuum polymerization apparatus, the chips obtained by the melt polymerization were subjected to solid phase polycondensation at 220 C. under a reduced pressure of 0.5 mmHg, to obtain chips of a solid phase polymerized polyester resin composition having an intrinsic viscosity of 0.76 dL/g and an acid value of 5 eq/ton.

(71) Hindered phenol compounds were added during the addition of a polycondensation catalyst in Example 19. Film was produced in the same manner as in Example 1.

(72) The results are shown in Table 5. From the results of Example 19 and Comparative Example 6, it was found that weather resistance can be further improved by introduction of hindered phenol structures in the case where the DMT method leading to excellent weather resistance and Sb/Ca/P/Li catalyst system were used.

Example 20 and Comparative Example 7

(73) A slurry of highly pure terephtalic acid and ethylglycol was successively fed to a first reactor for esterification in which reactant was previously contained, and esterification reaction was carried out at about 250 C. and 150 kPa (0.5 kg/cm.sup.2G) for 3 hours of average retention time under stirring. The reactant was sent to a second reactor for esterification, and esterification reaction was carried out to predetermined reaction degree at about 260 C. and 106 kPa (0.05 kg/cm.sup.2G) under stirring. In addition, each of a catalyst solution in which crystalline germanium dioxide was heated and dissolved in water, ethylene glycol was added thereto and heated, and a phosphate and ethylene glycol solution was successively fed to a second reactor for esterification. Esterified reaction product was successively fed to a first reactor for polycondensation, polycondensation was carried out at about 265 C. and 3300 Pa (25 torr) for 1 hour under stirring, then at about 265 C. and 400 Pa (3 torr) for 1 hour under stirring in a second reactor for polycondensation, and at about 275 C. and 60 to 100 Pa (0.5 to 0.8 torr) for 1 hour under stirring in a final reactor for polycondensation. Melted and polycondensed reactant was formed in the chips. Obtained chips were subjected to solid phase polymerization at 220 C. under a reduced pressure of 67 Pa (0.5 torr) using a rotation-type vacuum polymerization apparatus, to obtain chips of a polyester having an IV of 0.76 dL/g and an acid value of 5 eq/ton.

(74) The obtained Chips was dried to a moisture content of 15 ppm, and dried chips and silica particles having average particle diameter of 1.0 m were fed into a biaxial extruder equipped with a vent, melted and kneaded under deaeration to obtain a master batch containing silica particles of 10000 ppm. The obtained chips of a solid phase polymerized polyester, a master batch containing silica particles and a master batch containing a hindered phenol compound used in Example 17 were dried to a moisture content of 17 ppm, and film formation was carried out in the same manner as in Example 4 to prepare a film. The results are shown in Table 5. It was found that the similar effects were exhibited in use of a germanium catalyst.

Example 21 and Comparative Example 8

Production of Polyester (A)

(75) Trimellitic titanate was added to a mixture of dimethyl terephthalic acid and ethylene glycol such that the remaining concentration of titan element was 15 ppm, and the mixture was subjected to ester exchange reaction according to usual methods, to obtain an oligomer mixture. Silica particles having an average particle diameter of 1.0 m in an amount of 800 ppm was added to the oligomer mixture. Then, the temperature was elevated to 280 C. for 60 minutes while the reaction system was gradually decompressed to be 13.3 Pa (0.1 Torr), and polycondensed at 280 C. and 13.3 Pa until the intrinsic viscosity (IV) of a polyester was 0.55 dL/g. After pressure discharge, a resin under slight pressure was discharged in form of strands in cold water to rapidly cool, thereafter kept in cooled water for 20 seconds and cut them, to obtain chips having a size of about 3 mm in length and about 2 mm in diameter, shapes of cylinder and an intrinsic viscosity (IV) of 0.55 dL/g. Obtained pellets by melted polymerization were subjected to solid phase polymerization at 220 C. under a reduced pressure of 0.5 mmHg using a rotation-type vacuum polymerization apparatus to obtain chips of a solid phase polymerized polyester (A) having an intrinsic viscosity (IV) of 0.75 dL/g and an acid value of 6 eq/ton.

Production of Polyester (B)

(76) Dimethyl terephthalic acid and ethylene glycol were used as start raw materials and germanium dioxide was used as a catalyst, to obtain a polyester (B) containing orthophosphate of 1000 ppm and having an IV of 0.75 dL/g and an acid value of 6 eq/ton

(77) In Example 21, polyester (A), polyester (B) and a master batch containing a hindered phenol compound used in Example 17 were dried to a moisture content of 17 ppm. Film was formed in the same manner as in Example 4 to produce a film.

(78) In Comparative Example 8, film was produced in the same manner as in Example 21 except that a master batch containing a hindered phenol compound was not used.

(79) The results are shown in Table 5. From the results of Example 21 and Comparative Example 8, it was confirmed that effects were exhibited in the case where titan was used as a catalyst.

(80) TABLE-US-00005 TABLE 5 Comparative Comparative Comparative Example 19 Example 6 Example 20 Example 7 Example 21 Example 8 Hindered phenol IRG1330 IRG1010 IRG1010 compound Content of Hindered 200 0 200 0 200 0 phenol compound (ppm) Content of Hindered 0.77 0 0.68 0 0.68 0 phenol structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 1.2 1.3 1.3 glycol) IV of film (dL/g) 0.71 0.69 0.73 0.7 0.71 0.68 IV of raw material PET 0.76 0.76 0.76 0.76 0.75 0.75 (dL/g) AV of film (eq/ton) 7 10 8 12 10 13 AV of raw material PET 5 5 5 5 6 6 (eq/ton) Content of CT in film 0.4 0.4 0.4 0.4 0.35 0 (% by mass) Kind of Catalyst Sb/Ca/Li/P Sb/Ca/Li/P Ge Ge Ti Ti TOD 0.01 0.23 0.02 0.45 0 0 Polyester in resin 100 100 100 100 100 100 Result of HAST test 95 65 90 55 65 40 (105 C., 300 hr, %) Fracture elongation 1100 600 1000 600 800 500 retention half life at 160 C. (hr) Contamination of die A A A A A A lip, roll and the like IRG1330: Irganox 1330, manufactured by BASF Japan Ltd. IRG1010: Irganox 1010, manufactured by BASF Japan Ltd.

Example 22

Preparation of Master Batch Containing Fine Particles

(81) Chips of the solid phase polymerized polyester resin composition used in Example 2 were dried to a moisture content of 17 ppm. The chips of 50% by mass were mixed with rutile titanium dioxide of 50% by mass having an average particle diameter of 0.3 m (electron microscopy method). The mixture was fed to a biaxial extrude equipped with a vent, kneaded with deaeration, and extruded at 275 C. to prepare a master batch containing fine particles of rutile titanium dioxide (MB-1).

(82) (Preparation of Void Forming Agent)

(83) As raw materials, 20% by mass of polystyrene having melt flow rate of 1.5 (G797N manufactured by Japan PolyStyrene Inc), 20% by mass of polypropylene polymerized in gas and having melt flow rate of 3.0 (F300SP, manufactured by Idemitsu Kosan Co., Ltd) and 60% by mass of polymethylpentene having melt flow rate of 180 (TPX DX-820 manufactured by Mitsui Chemicals Inc) were mixed in form of pellets, fed to a biaxial extruder, and sufficiently kneaded, to prepare a void forming agent (MB-II).

(84) Chips of a solid phase polymerized polyester resin composition used in Example 2, MB-I and MB-II were mixed so as to be 80:12:8 (% by mass). The mixture was dried to a moisture content of 18 ppm, fed to an extruder, mixed and kneaded at 280 C., and extruded on a cooled drum controlled to 30 C. using T-die, to produce a non-drawn sheet. Next, the obtained non-drawn sheet was uniformly heated to 70 C. with heated rolls, and thereafter drawn at a ratio of 3.3 at 90 C. Subsequently, the obtained uniaxially drawn film was sent to a tenter, drawn at a ratio of 3.7 in a width direction at 140 C., heat-set at 220 C. for 5 seconds with width fixation, and further subjected to a relaxation treatment of 4% at 220 C. in the width direction, to obtain a void-containing white film having a thickness of 188 m.

Example 23

(85) A master batch containing fine particles (MB-III) was prepared in the same manner as in Example 22 except that a solid phase polymerized polyester resin composition was changed to a solid phase polymerized polyester resin composition obtained in Example 3.

(86) A void-containing white film was obtained in the same manner as in Example 22 except that chips of a solid phase polymerized polyester resin composition was changed to those obtained in Example 3 and a master batch containing fine particles (MB-I) was changed to (MB-III).

Comparative Example 9

(87) A master batch containing fine particles (MB-IV) was prepared in the same manner as in Example 22 except that a solid phase polymerized polyester resin composition was changed to chips of a solid phase polymerized polyester resin composition (without containing a hindered phenol compound) manufactured in Examples 4 to 10.

(88) A void-containing white film was obtained in the same manner as in Example 22 except that chips of a solid phase polymerized polyester resin composition was changed to those manufactured in Examples 4 to 10 and a master batch containing fine particles (MB-I) was changed to (MB-IV).

Example 24

(89) A white film was obtained in the same manner as in Example 22, except that 70% by mass of chips of a solid phase polymerized polyester resin composition obtained in Example 3 and 30% by mass of MB-III were used.

Example 25

(90) A raw material of (A) layer was prepared by mixing 50% by mass of chips of a polyester resin composition obtained Example 3 and 50% by mass of MB-III. A raw material composition of film of Example 23 was used as a raw material of (B) layer. Each of raw materials of (A) layer and (B) layer was fed to separative extruders, mixed and melted at 280 C., subsequently B layer in the melting state was joined on one side of A layer using a feedblock. At this time, delivery ratio of A layer and B layer was controlled using a gear pump. Then, layers were extruded on a cooled drum controlled at 30 C. using T-die, to prepare a non-drawn sheet so as to be A/B/A layers.

(91) (Production of Biaxially Drawn Film)

(92) The obtained non-drawn sheet was uniformly heated to 70 C. with heated rolls, and thereafter drawn at a ratio of 3.3 at 90 C. with rolls. Subsequently, the obtained uniaxially drawn film was sent to a tenter, drawn at a ratio of 3.7 in a width direction at 140 C., heat-set at 220 C. for 5 seconds with width fixation, and further subjected to a relaxation treatment of 4% at 220 C. in the width direction, to obtain a void-containing white film having a thickness of 188 m (19/150/19).

(93) The results of Examples 22 to 25 and Comparative Example 9 are shown in Table 6.

(94) TABLE-US-00006 TABLE 6 Comparative Example 22 Example 23 Example 24 Example 25 Example 9 Hindered phenol compound IRG1330 IRG1330 IRG1330 IRG1330 Content of Hindered 100 200 200 200 0 phenol compound (ppm) Content of Hindered 0.39 0.77 0.77 0.77 0 phenol structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 1.2 1.2 glycol) IV of film (dL/g) 0.71 0.71 0.71 0.71 0.67 IV of raw material PET 0.76 0.76 0.76 0.76 0.76 (dL/g) AV of film (eq/ton) 20 17 17 17 27 AV of raw material PET 5 5 5 5 5 (eq/ton) Content of CT in film (% 0.45 0.45 0.45 0.45 0.45 by mass) Kind of Catalyst Sb Sb Sb Sb Sb Result of HAST test 75 80 78 80 55 (105 C., 200 hr, %) Apparent specific gravity 1.1 1.08 1.13 1.1 Whiteness degree 86 87 91 92 86

Reference Example 1

(95) Chips of a polyester resin composition (without containing a hindered phenol compound) manufactured in Examples 4 to 10 were used as a raw material of A layer. Compositions of film raw material used in Example 7 were used as a raw material of B layer. Each of these raw materials of A layer and B layer was fed to separative extruders, mixed and melted at 280 C., subsequently B layer in melting state was joined on one side of A layer using a feedblock. At this time, delivery ratio of A layer and B layer was controlled using a gear pump. Then, layers were extruded on a cooled drum controlled at 30 C. using T-die, to prepare a non-drawn sheet so as to be A/B/A layers.

(96) (Production of Biaxially Drawn Film)

(97) The obtained non-drawn sheet was uniformly heated to 70 C. with heated rolls, and thereafter drawn at a ratio of 3.3 at 90 C. with rolls. Subsequently, the uniaxially drawn film was sent to a tenter, drawn at a ratio of 3.7 in a width direction at 140 C., heat-set at 220 C. for 5 seconds with width fixation, and further subjected to a relaxation treatment of 4% at 220 C. in the width direction to obtain a film having a thickness of 50 m (5/40/5).

(98) The results of weather resistance test (105 C., 300 hours) were 85% and good, but the film was whitened perhaps because crack was occurred on the surface from the beginning of elongation and appearance was poor.

Reference Example 2

(99) Film was obtained in the same as in Reference Example 1 except that raw materials of A layer and B layer were changed from Reference Example 1.

(100) The results of weather resistance test (105 C., 300 hours) were 55%, leading to poor weather resistance. This reason is because the main core layer of the film was poor in weather resistance and elongation cannot be realized by only a thin surface layer.

(101) From the results, polyester films of Examples shows more higher hydrolysis-resistance than that of a hydrolysis-resistance polyester film having conventionally low AV and high IV (for example, Comparative Examples 3 and 6).

(102) (Production of homoPET)

(103) Magnesium acetate tetrahydrate was added to a mixture of terephthalic acid and ethylene glycol such that the concentration in a polyester was 120 ppm in terms of a Mg atom, and the mixture was reacted at a temperature of 255 C. at normal pressure. Thereafter, thereto were further added antimony trioxide in such an amount that the concentration in the polyester was 250 ppm in terms of an Sb atom, cobalt acetate tetrahydrate in such an amount that the concentration in the polyester was 30 ppm in terms of a Co atom and trimethyl phosphate in an such an amount that the concentration in the polyester was 150 ppm in terms of a P atom, and the mixture was further reacted at a temperature of 260 C.

(104) Subsequently, the reaction product was transferred to a polycondensation reaction reactor, and silica particles having an average particle diameter of 1.0 m were added such that the concentration in the polyester was 800 ppm. Then, the reaction system was gradually decompressed while elevating the temperature by heating, and polymerized at 290 C. under a reduced pressure of 133 Pa (1 mmHg) according to usual methods, to obtain chips having an IV of 0.60 dL/g. Subsequently, using a rotation-type vacuum polymerization apparatus, solid phase polycondensation was conducted at 220 C. under a reduced pressure of 67 Pa (0.5 mmHg) to obtain a resin composition having an intrinsic viscosity of 0.76 dL/g and an acid value of 5 eq/ton. The content of a cyclic trimer (CT) was 0.29% by mass.

(105) (Production of Master Batch 1 Containing Hindered Phenol Compound)

(106) Chips of the homoPET were dried to a moisture content of 15 ppm, the chips and hindered phenol compound (Irganox (registered trademark) 1330) were fed into a biaxial extruder, decompressed with a vent, and melted and kneaded, to obtain a master batch 1 containing a hindered phenol compound of 50000 ppm.

Examples 26 to 29 and Comparative Examples 10 and 11

(107) A polyester resin composition was obtained by copolymerizing 3 mol % of neopentyl glycol (NPG) according to the manufacture of homoPET. A polyester resin composition had an intrinsic viscosity of 0.76 dL/g and an acid value of 5 eq/ton.

(108) Obtained chips of a polyester resin composition and a master batch 1 containing a hindered phenol compound were dry-blended. The mixture was dried to a moisture content of 17 ppm, fed to an extruder, and extruded in a sheet form from a die while the resin maximum temperature in an extruder melting part, a kneading part, a polymer tube, a gear pump and a filter was set at 290 C. and the resin maximum temperature in subsequent polymer tubes was set at 285 C. These polymers were each filtered using a filter medium of a stainless sintered body (nominal filtration accuracy: 20 m particle 95% cut). A flat die was set such that the resin temperature was 285 C. The extruded resin was wound around a casting drum having a surface temperature of 30 C., and solidified by cooling to prepare a non-drawn film.

(109) Next, the non-drawn film was heated to 100 C. with a group of heated rolls and an infrared heater, and thereafter drawn at a ratio of 3.3 in a longer direction by a group of rolls having a difference in circumferential speed, so that a uniaxially oriented PET film was obtained. Subsequently, the uniaxially oriented PET film was drawn at a ratio of 4.0 in a width direction at 130 C. in a tenter, heat-set at 235 C., and further subjected to a relaxation treatment at 200 C. in the width direction to obtain a biaxially oriented PET film having a thickness of 50 m.

(110) The results are shown in Table 7.

Comparative Example 12

(111) A polyester resin composition was obtained by copolymerizing 3 mol % of neopentyl glycol according to the manufacture of homoPET. A polyester film was produced in the same manner as in Example 26 using only the polyester resin composition, but the temperature was controlled such that the pressure of a polyester resin in each of film formation steps was comparable to that of Example 28. Specifically, the resin maximum temperature in an extruder melting part, a kneading part, a polymer tube, a gear pump and a filter was set at 300 C. and the resin maximum temperature in subsequent polymer tubes was set at 290 C.

(112) The results are shown in table 7. Although the intrinsic viscosity of film was the same as those of Examples, high temperature was required in film formation step since it was necessary to increase the intrinsic viscosity of a raw material polyester. As a result, decomposition was processed, and the acid value of the film was increased, leading to poor weather resistance.

(113) TABLE-US-00007 TABLE 7 Comparative Comparative Comparative Example 26 Example 27 Example 28 Example 29 Example 10 Example 11 Example 12 Copolymer component NPG NPG NPG NPG NPG NPG NPG (mol %) 3 3 3 3 3 3 3 Hindered phenol compound IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 Content of Hindered 30 60 200 400 5 2200 0 phenol compound (ppm) Content of Hindered 0.12 0.23 0.77 1.55 0.02 8.51 0 phenol structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 1.2 1.2 1.2 1.2 glycol) IV of film (dL/g) 0.72 0.73 0.73 0.73 0.69 0.73 0.73 IV of raw material PET 0.76 0.76 0.76 0.76 0.76 0.76 0.81 (dL/g) AV of film (eq/ton) 8 8 8 8 13 8 17 AV of raw material PET 5 5 5 5 5 5 4 (eq/ton) Content of CT in film (% 0.4 0.4 0.4 0.4 0.4 0.4 0.4 by mass) TOD 0.1 0.01 0.01 0.01 0.3 0.01 0.4 Result of HAST test 87 91 91 93 61 92 60 (105 C., 300 hr, %) Fracture elongation 900 1000 1100 1100 600 1000 600 retention half life at 160 C. (hr) Contamination of die A A A A A B A lip, roll and the like Thermal shrinkage 2 2 2 2 2 2 2 coefficient (%) 150 C. 30 min IRG1330: Irganox 1330, manufactured by BASF Japan Ltd.

Example 30

(114) A polyester resin composition was obtained by copolymerizing 3 mol % of isophthalic acid (IPA) according to the manufacture of homoPET. A polyester film was produced in the same manner as in Example 28 using chips of the polyester resin composition obtained and a master batch 1 containing a hindered phenol compound. The results are shown in Table 8.

Example 31

(115) A polyester resin composition was obtained by copolymerizing 3 mol % of 1,4-cyclohexane dimethanol (CHDM) according to the manufacture of homoPET. A polyester film was produced in the same manner as in Example 28 using chips of the polyester resin composition obtained and a master batch 1 containing a hindered phenol compound. The results are shown in Table 8.

Example 32

(116) A polyester film was prepared in the same manner as in Example 28 after homoPET, polyethylene naphthalate (IV=6.5 dL/g, AV=6) and a master batch 1 containing a hindered phenol compound were dry-blended. The results are shown in Table 8. Incidentally, NDC represents naphthalene dicarboxylic acid component.

Examples 33 to 35

(117) A polyester resin composition was obtained by copolymerizing each of 1.5 mol %, 5 mol % and 10 mol % of neopentyl glycol according to the manufacture of homoPET. The polyester resin composition obtained was dry-blended with a master batch 1 containing a hindered phenol compound, to prepare a polyester film in the same manner as in Example 28. Incidentally, in Example 35, the temperature was 225 C. for prevention of clip attachment during heat set. The results are shown in Table 8.

(118) TABLE-US-00008 TABLE 8 Example 30 Example 31 Example 32 Example 33 Example 34 Example 35 Copolymer component IPA CHDM NDC NPG NPG NPG (mol %) 3 3 3 1.5 5 10 Hindered phenol IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 compound Content of Hindered 200 200 200 200 200 200 phenol compound (ppm) Content of Hindered 0.77 0.77 0.77 0.77 0.77 0.77 phenol structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 1.2 1.2 1.2 glycol) IV of film (dL/g) 0.73 0.73 0.73 0.73 0.72 0.72 IV of raw material PET 0.76 0.76 0.76 0.76 0.76 0.76 (dL/g) AV of film (eq/ton) 8 8 8 8 8 8 AV of raw material PET 5 5 5 5 5 5 (eq/ton) Content of CT in film 0.4 0.4 0.4 0.4 0.4 0.4 (% by mass) TOD 0.01 0.01 0.01 0.01 0.01 0.01 Result of HAST test 91 90 92 89 91 91 (105 C., 300 hr, %) Fracture elongation 1100 1100 1100 900 1000 1000 retention half life at 160 C. (hr) Contamination of die A A A A A A lip, roll and the like Thermal shrinkage 2 2 2 2 2.4 5 coefficient (%) 150 C. 30 min IRG1330: Irganox 1330, manufactured by BASF Japan Ltd.

Example 36

(119) Chips of the homoPET were dried to a moisture content of 15 ppm, the chips and hindered phenol compound (Irganox 1010) were fed into a biaxial extruder, decompressed with a vent, and melted and kneaded, to obtain a master batch containing a hindered phenol compound of 50000 ppm (master batch 2 containing a hindered phenol compound).

(120) A polyester film was prepared in the same manner as in Example 28 except that a master batch 2 containing a hindered phenol compound was used as a master batch.

Example 37

(121) A polyester resin composition was obtained by copolymerizing 3 mol % of neopentyl glycol according to the manufacture of homoPET. The polyester resin composition had an IV of 0.70 dL/g and an acid value of 6 eq/ton. A polyester film was produced in the same manner as in Example 3 using chips of the polyester resin composition obtained and a master batch 1 containing a hindered phenol compound, but the temperature was controlled such that the pressure of a polyester resin in each of film formation steps was comparable to that of Example 3. Specifically, the resin maximum temperature in an extruder melting part, a kneading part, a polymer tube, a gear pump and a filter was set at 288 C. and the resin maximum temperature in subsequent polymer tubes was set at 285 C. The results are shown in Table 9. Weather resistance was inferior to that of Example 28 due to low molecular weight but results were good level.

Comparative Example 13

(122) A polyester resin composition was obtained by copolymerizing 3 mol % of neopentyl glycol according to the manufacture of homoPET. The polyester resin composition had an IV of 0.64 dL/g and an acid value of 5 eq/ton. A polyester film was produced in the same manner as in Example 37 using chips of the polyester resin composition obtained and a master batch 1 containing a hindered phenol compound. The results are shown in Table 9. Weather resistance was poor due to low molecular weight.

Comparative Example 14

(123) A polyester resin composition was obtained by copolymerizing 3 mol % of neopentyl glycol according to the manufacture of homoPET. The polyester resin composition had an IV of 0.76 dL/g and an acid value of 23 eq/ton. A polyester film was produced in the same manner as in Example 28 using chips of the polyester resin composition obtained and master batch 1 containing a hindered phenol compound. The results are shown in Table 9. Weather resistance was poor due to high acid value.

Example 38

(124) Magnesium acetate tetrahydrate was added into a mixture of terephthalic acid, ethylene glycol and neopentyl glycol such that the concentration in a polyester was 120 ppm in terms of a Mg atom, and the mixture was reacted at a temperature of 255 C. at normal pressure. Thereafter, thereto were further added antimony trioxide in such an amount that the concentration in the polyester was 250 ppm in terms of an Sb atom, cobalt acetate tetrahydrate in such an amount that the concentration in the polyester was 30 ppm in terms of a Co atom and trimethyl phosphate in an such an amount that the concentration in the polyester was 150 ppm in terms of a P atom, and the mixture was further reacted at a temperature of 260 C.

(125) Subsequently, the reaction product was transferred to a polycondensation reaction reactor, and hindered phenol compound (Irganox 1330) was added such that the concentration in the polyester was 200 ppm and silica particles having an average particle diameter of 1.0 m were added such that the concentration in the polyester was 800 ppm. Then, the reaction system was gradually decompressed while elevating the temperature by heating, and polymerized at 290 C. under a reduced pressure of 133 Pa (1 mmHg) according to usual methods, to obtain chips having an IV of 0.60 dL/g. Subsequently, using a rotation-type vacuum polymerization apparatus, solid phase polycondensation was conducted at 220 C. under a reduced pressure of 67 Pa (0.5 mmHg) to obtain a resin composition having an intrinsic viscosity of 0.76 dL/g and an acid value of 5 eq/ton. The content of a cyclic trimer (CT) was 0.3% by mass.

(126) Chips of a polyester resin composition obtained were dried to a moisture content of 17 ppm, to prepare a polyester film in the same manner as in Example 26. The results are shown in Table 9. Film having high weather resistance was obtained even when a hindered phenol compound was added during polycondensation of a polyester.

Example 39

(127) A solution of calcium acetate and ethylene glycol was added into a mixture of dimethyl terephthalate, dimethyl isophthalate and ethylene glycol such that the remaining concentration of calcium element was 200 ppm, and the mixture was subjected to ester exchange reaction according to usual methods, to obtain an oligomer mixture. Trimethyl phosphate was added to the oligomer mixture such that the remaining concentration of phosphorus element was 350 ppm, and stirred at 200 C. for 10 minutes in normal pressure under nitrogen atmosphere. Thereafter, the mixture of antimony trioxide and ethylene glycol solution, and lithium acetate and ethylene glycol solution was added thereto such that the remaining concentration of antimony element was 200 ppm and the remaining concentration of lithium element was 100 ppm. The mixture was further stirred at 250 C. for 10 minutes in normal pressure under nitrogen atmosphere. Then, the temperature was elevated to 280 C. for 60 minutes while the reaction system was gradually decompressed to be 13.3 Pa (0.1 Torr), and polycondensed at 280 C. under 13.3 Pa, to obtain chips made of a polyester having an IV of 0.58 dL/g.

(128) Subsequently, using a rotation-type vacuum polymerization apparatus, the chips obtained by the melt polymerization were subjected to solid phase polycondensation at 220 C. under a reduced pressure of 0.5 mmHg, to obtain chips of a copolymerized polyester resin composition having an intrinsic viscosity of 0.76 dL/g and an acid value of 5 eq/ton.

(129) A polyester film was prepared in the same manner as in Example 28 using chips of obtained polyester resin composition and a master batch 1 containing a hindered phenol compound. The results are shown in Table 9.

(130) TABLE-US-00009 TABLE 9 Comparative Comparative Example 36 Example 37 Example 13 Example 14 Example 38 Example 39 Copolymer component NPG NPG NPG NPG NPG IPA (mol %) 3 3 3 3 3 3 Hindered phenol compound IRG1010 IRG1330 IRG1330 IRG1330 IRG1330 IRG1330 Content of Hindered 200 200 200 200 200 200 phenol compound (ppm) Content of Hindered 0.68 0.77 0.77 0.77 0.77 0.77 phenol structure (eq/ton) Content of DEG (mol % in 1.2 1.2 1.2 1.2 1.2 1.2 glycol) IV of film (dL/g) 0.73 0.68 0.62 0.73 0.73 0.73 IV of raw material PET 0.76 0.7 0.64 0.76 0.76 0.76 (dL/g) AV of film (eq/ton) 8 8 7 27 8 7 AV of raw material PET 5 6 5 23 5 5 (eq/ton) Content of CT in film (% 0.4 0.4 0.4 0.9 0.4 0.4 by mass) TOD 0.01 0.01 0.01 0.01 0.01 0.01 Result of HAST test 92 87 55 20 91 92 (105 C., 300 hr, %) Fracture elongation 1100 1000 600 700 1000 1100 retention half life at 160 C. (hr) Contamination of die A A A A A A lip, roll and the like Thermal shrinkage 2 2 2 2 2 2 coefficient (%) 150 C. 30 min IRG1010: Irganox 1010, manufactured by BASF Japan Ltd. IRG1330: Irganox 1330, manufactured by BASF Japan Ltd.

Example 40

Production of Master Batch Containing Fine Particles

(131) Chips of the copolymerized polyester resin composition used in Example 28 were dried to a moisture content of 17 ppm. The chips of 49.6% by mass and a master batch containing a hindered phenol compound of 0.4% by mass were mixed with rutile titanium dioxide of 50% by mass having an average particle diameter of 0.3 m (electron microscopy method). The mixture was fed to a biaxial extrude equipped with a vent, kneaded with deaeration, and extruded at 275 C., to prepare a master batch containing fine particles of rutile titanium dioxide (MB-IV).

(132) (Preparation of Void Forming Agent)

(133) As raw materials, 20% by mass of polystyrene having melt flow rate of 1.5 (G797N manufactured by Japan PolyStyrene Inc), 20% by mass of polypropylene polymerized in gas and having melt flow rate of 3.0 (F300SP, manufactured by Idemitsu Kosan Co., Ltd) and 60% by mass of polymethylpentene having melt flow rate of 180 (TPX DX-820 manufactured by Mitsui Chemicals Inc) were mixed in form of pellets, fed to a biaxial extruder, and sufficiently kneaded, to prepare a void forming agent (MB-V).

(134) Chips of the solid phase polymerized polyester resin composition used in Example 28, a master batch 1 containing a hindered phenol compound, MB-IV and MB-V were mixed so as to be 80:0.32:12:8 (mass ratio). The mixture was dried to a moisture content of 18 ppm, fed to an extruder, mixed and kneaded at 280 C., and extruded on a cooled drum controlled to 30 C. using T-die to produce a non-drawn sheet. Next, the obtained non-drawn sheet was uniformly heated to 70 C. with heated rolls, and thereafter drawn at a ratio of 3.3 at 90 C. Subsequently, the uniaxially drawn film was sent to a tenter, drawn at a ratio of 3.7 in a width direction at 140 C., heat-set at 220 C. for 5 seconds with width fixation, and further subjected to a relaxation treatment of 4% at 220 C. in the width direction to obtain a void-containing white film having a thickness of 188 m. The results are shown in Table 10.

Comparative Example 15

(135) A void-containing white film was obtained in the same manner as in Example 40 except that a master batch 1 containing a hindered phenol compound was not added during production of a master batch containing fine particles and film formation. The results are shown in Table 10.

Example 41

(136) Chips of the solid phase polymerized polyester resin composition used in Example 28, a master batch 1 containing a hindered phenol compound and MB-IV were mixed so as to be 70:0.28:30 (mass ratio). The mixture was dried to a moisture content of 18 ppm, fed to an extruder, mixed and kneaded at 280 C., and extruded on a cooled drum controlled to 30 C. using T-die, to produce a non-drawn sheet. Next, the obtained non-drawn sheet was uniformly heated to 70 C. with heated rolls, and thereafter drawn at a ratio of 3.3 at 90 C. Subsequently, the uniaxially drawn film was sent to a tenter, drawn at a ratio of 3.7 in a width direction at 140 C., heat-set at 220 C. for 5 seconds with width fixation, and further subjected to a relaxation treatment of 4% at 220 C. in the width direction, to obtain a white film having a thickness of 188 m. The results are shown in Table 10.

(137) TABLE-US-00010 TABLE 10 Comparative Example 40 Example 15 Example 41 Copolymer component NPG NPG NPG (mol %) 3 3 3 Hindered phenol compound IRG1330 IRG1330 Content of Hindered phenol 200 0 200 compound (ppm) Content of Hindered phenol 0.77 0 0.77 structure (eq/ton) Content of DEG 1.2 1.2 1.2 (mol % in glycol) IV of film (dL/g) 0.71 0.66 0.71 IV of raw material PET (dL/g) 0.76 0.76 0.76 AV of film (eq/ton) 17 28 16 AV of raw material PET 5 5 5 (eq/ton) Content of CT in film (% by 0.45 0.45 0.45 mass) Result of HAST test (105 C., 80 53 79 200 hr, %) Apparent specific gravity 1.11 1.1 Whiteness degree 90 90 88 IRG1330: Irganox 1330, manufactured by BASF Japan Ltd.

(138) When the polyester film is used for the back sheet of the solar cell, a film of Examples is bonded and laminated with, a barrier film, electric insulation film, a light reflection layer and the like as necessary to form a back sheet. The solar cell back sheet obtained can be formed into a solar cell module by packing an electromotive cell of crystalline silicon, amorphous silicon or the like between the sheet and a surface base material such as glass or the like via a filler such as EVA or the like. The obtained solar cell can accomplish much high durability.

INDUSTRIAL APPLICABILITY

(139) The polyester film of the present invention has high weather resistance, and can be used in various applications that require weather resistance, particularly hydrolysis resistance. Examples of specific applications include those of a front sheet (light receiving surface) and back sheet (opposite to the light receiving surface) of a solar cell, motor insulation, and a capacitor, and particularly the polyester film is suitably used for the back sheet of the solar cell.