JPS62189133A - Manufacture of polyester film - Google Patents

Abstract

PURPOSE:To enable the titled method to provide a high-quality film which possesses no surface defect and is superior in uniformity of thickness at high speed, by a method wherein a polyester composite having an initially- accumulated quantity of electric charge of a specific molten polymer is melted and extruded in a filmy state, the film is stuck close to a rotary cooling roll electrostatically and cured by quenching. CONSTITUTION:It is necessary that a polyester composite has an initially- accumulated quantity of an electric charge at more than 2.9muc/mm<2> and heat resistance at less than 0.210. It is not desirable as high speed electrostatic adhe sion can't be given and it becomes difficult to manufacture a high-quality film, whose surface is free from a defect and uniformity in thickness is high, at high speed when the initially-accumulated quantity of electric charge is less than 2.0muc/mm<2> and as it becomes difficult to reuse an edge part or off- specification film, which is generated at a stretching process, by melting the same when the heat resistance exceeds 0.210. This film is desirable in that stretching of the same more than 1.1 times unidirectionally at least improves dynamic properties and other plysical properties and is provided for various uses.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application 111F) The present invention relates to a method for producing a polyester film with excellent thickness uniformity with high efficiency.

(Prior art) Saturated linear polyesters, represented by polyethylene terephthalate, have excellent mechanical properties, heat resistance, weather resistance, electrical insulation properties, chemical resistance, etc., and are therefore used for packaging, photography, etc.
It is widely used in a wide range of fields such as electrical applications and magnetic tape. Polyester films are usually obtained by melt-extruding polyester and then biaxially stretching it. in this case,
In order to improve the uniformity of film thickness and casting speed, it is necessary to improve the adhesion between the sheet and the drum surface when the sheet is melted and extruded from the extrusion nozzle and rapidly cooled on the surface of the rotating cooling drum. Must be.

As a method of increasing the adhesion between the sheet-like material and the drum surface, a wire-shaped electrode is installed between the extrusion die and the rotating cooling drum, and a high voltage is applied to deposit static electricity on the top surface of the unsolidified sheet-like material. It is known that a method of rapidly cooling the sheet while closely contacting the surface of the cooling body (hereinafter referred to as electrostatic contact casting method) is effective (for example, Japanese Patent Publication No. 37-6
142).

Uniformity of film thickness is an extremely important characteristic of film quality, and film productivity is directly dependent on casting speed, so increasing casting speed is extremely important to improve productivity. ,
Great efforts are being made to improve electrostatic adhesion.

It is known that increasing the amount of charge on the surface of a sheet-like object is an effective means for improving electrostatic adhesion.

In addition, in order to increase the amount of charge on the surface of a sheet material in the electrostatic contact casting method, the polyester raw material used in the production of polyester film is modified to have a specific resistance (hereinafter simply referred to as specific resistance) when the polyester is melted. It is known that it is effective to lower the ratio (for example, Japanese Patent Publication No. FLF853-40231).

It is true that electrostatic adhesion can be improved by lowering the specific resistance. However, as is clear from Figure 1, up to a maximum casting speed of around 50 m/min, and a resistivity of approximately 0.2 x 10'Ω/min, the maximum casting speed increases greatly as the resistivity decreases; is 50 m/min or more, the specific resistance is 0.
In the region of 2×10'Ω·m or less, a slight decrease in resistivity causes a large change in maximum casting speed. For example, the difference in resistivity between maximum casting speeds of 70 m/min and 80 m/min is only 0.01 x 10'Ω°α. However, the curve in Figure 1 is drawn as an average value based on a large number of experimental data. In reality, the correlation between maximum casting speed and specific resistance becomes very poor in the region of 50 m/min or more. This means that the maximum casting speed is 5
If the specific resistance is 0 m/min or more and the specific resistance is about 0.2 x 10 Ω·m or less, this indicates that simply lowering the specific resistance is insufficient as a means for improving electrostatic adhesion.

Electrostatic adhesion is caused by electrostatic attraction between the sheet and the rotating cooling roll, and this electrostatic attraction is proportional to the amount of charge generated on the surface of the sheet.

Therefore, an important point for improving electrostatic adhesion is how to increase the amount of charge generated on the surface of the sheet-like material.

The amount of charge generated on the surface of the sheet-like material largely depends on the high voltage application conditions, that is, the electrode structure, the distance between the electrode and the rotary cooling ring and extrusion die, the applied voltage, and the electrical properties of the raw material polyester. Although lowering the specific resistance is one of the necessary conditions for increasing the amount of charge on the surface of this sheet-like material, it is thought that the above-mentioned phenomenon occurs because the sufficient condition is not satisfied.

That is, in order to generate electric charges on the surface of the sheet-like object, ions generated inside the sheet must move to the surface of the sheet-like object, and for this purpose, it is necessary to lower the specific resistance of the sheet-like object. Therefore, by lowering the specific resistance, it is possible to improve electrostatic adhesion. However, even if the resistivity is lowered to make it easier for ions to move to the surface of the sheet, if the movement is slow, the charge will be neutralized on the surface of the sheet, and as a result, the amount of surface charge will not increase. In the region of high electrostatic adhesion, simply lowering the resistivity is insufficient.

Therefore, the present inventors have made extensive efforts to establish a method for evaluating the electrical properties of polyester raw materials that corresponds to the amount of electric charge generated on the surface of a sheet-like material. It was discovered that the amount of accumulated charge (hereinafter simply referred to as initial accumulated charge amount) is suitable for this purpose, and the present invention was completed. That is, it has been found that extremely high electrostatic adhesion can be imparted by increasing the initial accumulated charge amount of the polyester as determined by the measuring device shown in FIG. 2 to a specific value or more.

The initial accumulated charge amount was measured by the following method.

A sample was sandwiched between electrodes placed in parallel at a distance of 1 crn, set in a constant temperature bath 4 maintained at 275°C by a temperature controller 5, and a voltage of 1200 V was applied for 3 minutes by a switch circuit 2 using a high voltage power supply 1. The voltage and current values at the time are detected by a voltage detection circuit and a current detection circuit 7, converted into digital values by an A/D converter 8, and then recorded as data 10 by a data processing device 9. An example of voltage and current characteristics obtained by this method is shown in FIG.

The initial current value (io) is the value corresponding to the specific resistance, and l
c is the charging current and it is the conduction current. Furthermore, area A is the amount of accumulated charge accumulated at the electrode interface, and area A is the amount of charge dissipated at the electrode.

Electrostatic adhesion is caused by electrostatic attraction between the sheet material and the rotary cooling roller. This electrostatic attraction is considered to be proportional to the amount of charge generated on the surface of the sheet-like object. If the electrostatic adhesion method is carried out under the same conditions, it is expected that the amount of charge generated on the surface of the polyester sheet material, which has a large amount of accumulated charge, will increase. Therefore, it is expected that electrostatic adhesion will be improved by increasing the amount of accumulated charge. Therefore, the inventors of the present invention paid attention to the amount of accumulated charge.

The amount of accumulated charge can be determined from the area A in FIG.

However, in the measurement using the method of the present invention, the decay rate of the charging current is slow, and it takes about 3 minutes for the charging current to decay completely. On the other hand, in the actual electrostatic close-contact casting method, the time from the time the charge is attracted to the time it comes into close contact with the cooling roll is extremely short, and the amount of accumulated charge determined from the area A does not actually match. The amount of charge accumulated in an extremely short period of time is important. The time from when the charge is attracted until it comes into close contact with the cooling roll is called the amount, although it varies depending on the position of the electrode and the casting speed.

), and developed the present invention. The reason why the actual electrostatic contact casting method took a slightly longer time is because the applied voltage in the measurement using the method of the present invention is approximately one order of magnitude lower than that in the actual electrostatic contact casting method.

The initial accumulated charge amount was determined as shown in FIG.

In other words, the amount of accumulated charge (μ
C) was divided by the electrode area (-) and expressed as μC/-.

FIG. 4 is illustrated to make it easier to understand the usefulness of the method of the present invention. A and B in FIG. 4 show a case in which the initial current value (10) is the same, but there is a large difference in the change in current value over time. That is, a person is a typical example in which the proportion of initial accumulated charge is high, and B is a typical example in which the proportion of consumed charge is conversely high.

The initial current value (1o) is a value corresponding to specific resistance, and in terms of specific resistance, there is no difference in electrostatic adhesion between the two resins. However, the actual maximum casting speed is higher in A, and the amount of initial accumulated charge can be said to be a better measure than the specific resistance. Furthermore, as shown in FIG. 1, there is a good correlation between the initial accumulated charge amount and the maximum casting speed. In particular, unlike in the case of conventionally known resistivity, the slope of the correlation between the two is large in regions where the maximum casting speed exceeds 50 s/min and electrostatic adhesion is highly high, indicating that this is a particularly useful measure in this region. . On the other hand, in the range of maximum casting speed of 50 m/min or less, resistivity is a more effective measure, and it can be said that they have a complementary relationship with the initial accumulated charge amount after the maximum casting speed reaches 50 m/min.

Electrostatic adhesion is caused by electrostatic attraction between the sheet-like material and the rotating cooling roll, and this electrostatic attraction is considered to be proportional to the amount of charge generated on the surface of the sheet-like material. Although the initial accumulated charge amount was not a direct measurement of the amount of charge generated on the surface of the sheet material during electrostatic close-contact casting, it is believed that the good result was obtained because there is a good correlation between the two amounts of charge. Conceivable. .

Moreover, a polyester film cannot be said to have sufficient quality characteristics just by having a high uniformity in thickness; it must have excellent heat resistance. Poor heat resistance is undesirable because it becomes difficult to melt and reuse film edges and non-standard film produced during the stretching process.

(Problems to be Solved by the Invention) The present invention improves the above-mentioned drawbacks, improves the electrical properties of the polyester raw material used in the production of polyester films by electrostatic adhesion casting, and improves the electrical properties of the polyester raw material to be free from surface defects.
It is an object of the present invention to provide a method capable of forming a high-quality polyester film with excellent thickness uniformity at high speed.

(Means for Solving the Problems) The present invention involves melt-extruding into a film a polyester composition whose initial accumulated charge amount of the molten polymer is 2.9 μc/d or more as measured by the method defined in the text. This method of producing a polyester film is characterized in that the melt-extruded film is then electrostatically brought into close contact with a rotary cooling wheel and rapidly solidified.

A preferred embodiment (1) of the present invention is a method for producing a polyester film using a polyester composition having a heat resistance of 0.210 or less as measured by the method described in the text.

A more preferred embodiment (2) of the present invention is a method for producing a polyester film according to any one of the above invention and embodiment (1), in which the polyester film is further stretched by 1.1 times or more in at least one direction.

The polyester of the present invention has 80 mol% of its repeating units.
The above is composed of ethylene terephthalate, and other copolymerized components include isophthalate full, p-β-oxyethoxybenzoic acid, 2.6-naphthalene dicarboxylic acid, 4.4'-dicarboxyl diphenyl, and 4.4 '−
Dicarboxylbenzophenone, bis(4-carboxylphenyl)ethane, adipic acid, sebacic acid, 5-
Examples include dicarboxylic acid components such as sodium sulfoisophthalate.

As the glycol component, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimetatool, ethylene oxide adduct of bisphenol A, etc. can be arbitrarily selected and used. In addition, small amounts of amide bonds, urethane bonds, ether bonds, carbonate bonds, etc. may be included as copolymer components.

The polyester composition used in the method of the present invention has an initial accumulated charge amount of 2.9 μc/mm2 or more, preferably 3 μc/mm2 or more.
．． 3μc/mm2 or more, more preferably 4.1μ(+/
It needs to be at least mJ. Initial accumulated charge amount is 2.9μ
If it is less than C/-, high-speed electrostatic adhesion cannot be imparted, and a high-quality film with no surface defects and highly uniform thickness cannot be formed at high speed, which is not preferable.

Further, the polyester composition used in the method of the present invention must have a heat resistance of 0.210 or less, preferably 0.190 or less, and more preferably 0.17θ or less. If the heat resistance exceeds 0.210, it is not preferable because it becomes difficult to melt and reuse the selvedge portions and non-standard film produced in the stretching process.

Further, the film used in the method of the present invention is an unstretched film, -
Either an axially stretched film or a biaxially stretched film may be used, but stretching the film in at least one direction by a factor of 1.1 times or more, preferably by a factor of 2.5 times or more improves the mechanical properties and other physical properties, making it suitable for various uses. preferred for serving.

The polyester composition used in the method of the present invention is not particularly limited as long as it satisfies the engineering conditions; for example, polyester produced by a transesterification method may be used, or polyester produced by a direct polymerization method may be used. Good too. Further, polyester manufactured in a batch manner may be used, or polyester manufactured in a continuous manner may be used.

Furthermore, it may contain a lubricant made of inorganic or organic fine particles, and if the above requirements are met, it may contain particles that precipitate during the polyester manufacturing process, so-called internal particles.

A polyester composition that satisfies the above requirements contains an Mg compound and p
This can be achieved by incorporating the compound in polyester in a solubilized form. Furthermore, this can be easily achieved by using a Ca compound, a Sr compound, a Na compound, a K compound, a Co compound, a Zr compound, etc. in combination. More specifically, it is a composition containing Mg and p compounds solubilized in polyester in amounts that simultaneously satisfy the following general formula.

30≦Mg≦400...CI) 0.8
≦Mg/p≦3...(I[) [In the formula, Mg is the content (ppm) of the Mg compound as an Mg atom with respect to the polyester, and Mg/p is the atomic ratio. ] More preferred is a polyester composition containing an alkali metal compound solubilized in polyester in an amount satisfying the following general formula.

3≦Cloudy≦50 (III) Another preferred composition is a polyester composition that simultaneously satisfies the above formulas (I) and (II), or 1IfTE (
In the polyester composition that simultaneously satisfies formulas I), (II), and (I[), C solubilized in the polyester is further added.
.

This is a polyester composition containing a compound and a p-compound in amounts that simultaneously satisfy the following general formula.

3.0≦Co≦50 −(IV)0.8
≦(Mg+Co)/P≦a ・(V) [in the formula,
Co is C for polyester of Co compound.

Content as atoms (ppm), (Mg + Co)
/p indicates the atomic ratio. ] Another preferred composition is a polyester composition that satisfies the above formulas (I) and (TI) at the same time, or a polyester composition that satisfies the above formulas (I) and (TI) at the same time;
), (n), and (III), which further contains a polyester-solubilized metal and a p-compound in amounts that simultaneously satisfy the following general formulas.

30≦Mg+M2≦400...(Vl)
2≦Mg /M2≦100 ... (■) 0
．． 8≦(Mg +M2) / p≦3...
(■) [In the formula, Mg is the content (ppm) of the Mg compound as an Mg atom in the polyester, M is Ca5
The content (ppm) of at least one alkaline earth metal compound selected from Cr and Ba compounds as metal atoms in the polyester, Mg/M'z and (Mg+M!)/p are the respective atomic ratios. shows. ] Other preferred compositions include the above (I) and (II).
), (Vl), (■), (■) formulas simultaneously, or the above-mentioned (I), (II), (I
[), (Vl), (■), (■) A polyester composition that further contains a Co compound and a p compound solubilized in polyester in an amount that simultaneously satisfies the following general formula. It is a thing.

3.0≦Co≦50 =-(IX)0
．． 8≦(Mg + Mz + Co) / p≦a
-(X) [Wherein, co is C for polyester of Co compound.

Content as atoms (ppm), (Mg+Mz −) −
Co)/p indicates the atomic ratio. ] Another preferred composition is a polyester composition that satisfies the above formulas (I) and (II) at the same time, or a polyester composition that satisfies the above formulas (I) and (II) at the same time;
), (II), and (I[), and further contains a solubilized Zr compound and a p compound in the polyester in an amount that simultaneously satisfies the following general formula.

3.0≦Zr≦19 ・(XI)0.
8≦(Mg+Zr)/p≦3 −(X[[) [wherein, zr is the content (ppm) of the Zr compound as a Zr atom in the polyester, (Mg + Zr) /
p indicates an atomic ratio. ] Other preferred compositions include the above (I), (n), and (I).
V), a polyester composition that simultaneously satisfies formula (■),
Or the above (I), (II), (I[), (IV),
A polyester composition that simultaneously satisfies formula (V) further contains a Zr compound and a p compound solubilized in polyester in an amount that simultaneously satisfies the following general formula.

3.0≦Zr≦19...(XI)0
, s≦(Mg+Co+Zr)/p≦a −(x
tv) [In the formula, zr is the content (ppm) of the Zr compound as a Zr atom in the polyester, (Mg + Co
10Zr)/p indicates the atomic ratio. ] Other preferred compositions include the above (1), (It), and (
A polyester composition that simultaneously satisfies the formulas VI), (■), and (■), or the above-mentioned (I), (II), (I[),
In a polynisder composition that simultaneously satisfies formulas (VI), (■), and (■), Z solubilized in polyester is further added.
This is a polyester composition containing an r compound and a p compound in an amount that simultaneously satisfies the following general formula.

3.0≦Zr≦19 −= (XV)
0.8≦(Mg+M2+Zr)/p≦3 ・(
XVI) [In the formula, ZR contains KL (PPM) as ZR atoms for the ZR compound polyester, (MG +)
M2+Zr)/p indicates the atomic ratio. ] Other preferred compositions include the above (I), (II), (
VI), (■), (■), (IX), a polyester composition that simultaneously satisfies (X) formulas, or the above (I),
II), (III), (Vi), (■), (■), (I
A polyester composition that simultaneously satisfies formulas X) and (X) further contains a Zr compound and a p compound solubilized in polyester in an amount that simultaneously satisfies the following general formula.

3.0≦Zr≦1 9 −(XV
[)0.8≦(Mg+Mz1Co+Zr)/p≦3
・(XVI)c In the formula, zr is the content (ppm) of the Zr compound as a Zr atom in the polyester, (M
g + M2 + Co + Zr)/p indicates the atomic ratio. ] Gradient The composition is not necessarily limited to the above-mentioned compositions as long as it satisfies the above requirements.

In the method of the present invention, there are no limitations on the structure of the electrostatic force applying device or the electrostatic force applying conditions, and they may be set arbitrarily. For example, the structure of the electrostatic force applying device is the electric structure, the presence or absence of a counter electrode, the positional relationship between the electrode and counter electrode, the extrusion port, the cooling roll, etc., and the electrostatic force applying conditions are such that the set voltage and current value can be arbitrarily set. good.

(Example) Next, Examples and Comparative Examples of the present invention will be shown. All parts in the examples mean parts by weight unless otherwise specified.

The measurement waves used are shown below.

(1) Esterification rate is determined from the presence of carboxyl groups remaining in the reaction product and the saponification value of the reaction product.

(2) Intrinsic viscosity Home IJmer is dissolved in a mixed solvent of phenol (6 parts by weight) and tetrac tetraethane (4 parts by weight) and measured at 30°C.

(3) Melting specific resistance of polymer Place two electrode plates in polyester melted at 275°C, apply a voltage of 120 V, measure the current value (io), and calculate the specific resistance value (ρl) using the following formula. Find it by

ρi (Ω・cIn)=-X7 A-electrode area (c!l), t=interelectrode distance (cfn)
■=Voltage (■) (4) Electrostatic adhesive pressing/f$'4- A tungsten wire electrode is provided between the mouthpiece of the machine and the cooling drum, and a voltage of 10 to 15 KV is applied between the electrode and the casting drum. Casting is carried out by applying a .

The higher the casting speed of the polymer, the better the electrostatic adhesion.

(5) Heat-resistant polymer The polymer is sealed in a glass ampoule under a nitrogen vacuum of 100IIIHf, and the change in intrinsic viscosity is measured when heat-treated at 300° C. for 4 hours. Heat resistance is expressed as a decrease in intrinsic viscosity (ΔXV) due to heat treatment. The smaller ΔIV is, the better the heat resistance is.

(Example 1) A first esterification reactor equipped with a stirring device, a partial condenser, a raw material inlet, and a product outlet, the inside of the reaction vessel was divided into two hinoki, each reaction vessel was equipped with a stirring device, An 8-stage complete mixing continuous esterification reactor was used, which consisted of a second esterification reactor equipped with a condenser, a raw material inlet, and a product outlet.

An EG slurry of TPA adjusted to a molar ratio of ethylene glycol (EG) to terephthalic acid (TPA) of 1.7 was continuously supplied to the system in which the esterification reaction product of the first esterification reactor existed. At the same time, TPA's EG
An EG solution of acetylated magnesium tetrahydrate and a PG solution of zirconyl acetate are passed through the reaction vessel through a supply port separate from the slurry supply port. It was continuously supplied at a concentration of 15 ppm, and the reaction was carried out at normal pressure for an average residence time of 4.5 hours and at a temperature of 255°C.

This reaction product was continuously taken out of the system, supplied to the first tank of the second esterification reactor, and continuously taken out from the second tank. An overflow type was used for transfer from the first tank to the second tank.

A KG solution of antimony trioxide in an amount such that 0.9 parts by weight of EG and 250 ppm as sb atoms and 48 ppm as p atoms based on the polyester unit in the reaction product passing through the reaction vessel. In the first tank, a solution of IBG containing trimethyl phosphate in an amount such as
An EG solution of sodium acetate in an amount such that pm and an EG solution of trimethyl phosphate in an amount such that p atoms are 86 ppm - Continuously supplied to the second tank and at normal pressure for various average residence times 2.5 hours, temperature 260℃
I reacted with

The esterification rate of the reaction product in the first esterification reactor is 7
0%, and the esterification rate of the reaction product in the second esterification reactor was 98%.

The esterification reaction product was continuously filtered through a stainless steel wire mesh filter with an opening of 400 mesh, and then subjected to a two-stage continuous polycondensation reaction equipped with a stirring device, a partial condenser, a raw material inlet, and a product outlet. Polyester (4
) was obtained. The initial accumulated charge amount of this polymer is 6.53μ
a/vd, maximum casting speed was 72 m/min, and heat resistance was 0.139.

Further, Table 1 shows the properties of the film obtained when the above raw materials were used and the film forming rate was increased while keeping the film thickness constant under the following conditions.

Film forming conditions Film thickness: 12μ (after biaxial stretching) Extrusion temperature = 290°C Electrostatic adhesion conditions: 0.25m9S US electrode, applied voltage 10-15KV Longitudinal stretching ratio = 3.5x Longitudinal stretching temperature: 90°C Horizontal Stretching ratio: 3.5 times Transverse stretching temperature: 130°C Heat setting temperature = 220°C As can be seen from the results in Table 1, polyester (A) is 2+5
A high quality film can be obtained even if the film is formed at a take-off speed of m/min.

(Comparative Example 1) Using a method similar to the method for producing polyester (A) in Example 1, an EC solution of magnesium acetate tetrahydrate as a metal compound was added to the first ester reaction vessel so that the concentration of Mg atoms was 120 ppm. EC solution of antimony trioxide
The EC solution of cobalt acetate tetrahydrate was added to the first tank of the second esterification reactor so that the concentration of B atoms was 250 ppm.
The EC solution of trimethyl phosphate was added to the second tank of the second esterification reactor so that the concentration of o atoms was 30 ppm, and the EC solution of trimethyl phosphate was added as a p compound to 140 ppm as p atoms.
The polyester (B) having an intrinsic viscosity of 0.620 was obtained by changing the method so that it was continuously supplied to the first tank of the second esterification reactor so that the following was achieved. The initial accumulated charge of this polymer is 2
．． 12μc/ld, maximum casting speed is 4zm/
The heat resistance was 0.145. In addition, Table 1 shows the properties of the film obtained using the above raw materials in the same manner as in Example 1.
It was shown to. As can be seen from the results in Table 1, polyester)
If the film is formed at a take-up speed of 175yy+ 7 minutes or more, only an extremely low-quality film with no commercial value will be obtained. (Effects of the Invention) When polyester film is produced by the method of the present invention, there will be no surface defects and the thickness will be uniform. Since a high-quality polyester film with excellent properties can be formed at high speed, its economic value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the maximum casting speed, the amount of charge accumulation, and the specific melting resistance. FIG. 2 is a schematic diagram showing a method for measuring the amount of charge accumulated in a molten polymer according to the present invention. Reference numeral 1 in Fig. 2, High voltage 'l'li source (1200v) 2, Switch circuit (high voltage transistor) that can be turned on and off by a signal from the microcomputer ('I) 3, Electrode and sample 4, Constant temperature chamber (275℃) 5. Temperature controller 6, Current detection circuit 7, Voltage detection circuit 8, A/D converter 9, Data processing device (microcomputer) 10. Data output device Figures 3 and 4 are the same as in Figure 2. This is a representative example of voltage and current characteristics determined using the device. Patent applicant Tei Toyobo Co., Ltd. 7 Figures 3″ @ Time (17th year of junior high school) nM (juice) Procedural amendment May 17, 1985 1 Indication of case Patent application dated June 2, 1985 (1) Name of the invention Method for manufacturing polyester film & Relationship with the case of the person making the amendment Patent applicant 2-2-8 Dojimahama, Kita-ku, Osaka (316) Toyobo Co., Ltd. 1)” is corrected. (2) On page 12, line 16, "high-speed" is corrected to "advanced." Procedural amendment old (spontaneous) j', :j Iris April 21, 1988 Director General of the Patent Office Michibe Uga, Indication of the case 1985 Patent Application No. 94882 2 Name of the invention Process for manufacturing polyester film 3 , Relationship with the case of the person making the amendment Patent applicant 2-2-8 Dojimahama, Kita-ku, Osaka (31G) Column 5 of the detailed explanation of the invention in the specification of Toyobo Co., Ltd. Item 4 of the detailed description of the contents of the amendment Correct the explanation column as follows. (3) On page 19, line 6, "gradient" is corrected to "of course." (4) On page 27, line 8, "charge accumulation amount" is corrected to "initial accumulation charge amount". (5) On page 27, lines 10 and 11, "charge accumulation amount" is corrected to "initial accumulation charge amount". Procedural amendment (formality) 1. Description of the case 1985 Patent Application No. 94882 2 Name of the invention Method for manufacturing polyester film 3 Person making the amendment Relationship to the case Patent applicant Toyobo Co., Ltd., 2-2-8 Dojimahama, Kita-ku, Osaka (31B) Company Information 1, Subject of Amendment Written Amendment to Procedures Submitted on April 21, 1986 (1) The column on Subject of Amendment in the written amendment (voluntary) submitted on April 21, 1986 is corrected as shown in the attached sheet. (2) Written amendment submitted on April 21, 1986 (voluntary)
In the first and second lines of the content of the amendment, "The column for detailed explanation of the invention in the specification is corrected as follows." is changed to "The column for detailed explanation of the invention in the specification is corrected as follows." ” is corrected.

Claims (3)

[Claims] (1) Melt-extrude a polyester composition in which the initial accumulated charge of the molten polymer is 2.9 μc/mm^2 or more as measured by the method defined in the text, and then cool the melt-extruded film by rotation. A method for producing a polyester film, characterized by electrostatically adhering it to a roll and rapidly solidifying it. (2) A method for producing a polyester film according to claim 1, using a polyester composition having a heat resistance of 0.210 or less as measured by the method defined herein. (3) A method for producing a polyester film, which further stretches the polyester film according to any one of claims 1 to 2 by a factor of 1.1 or more in at least one direction.