JPH0645175B2 - Method for producing polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polyester film having excellent thickness uniformity with high efficiency.

(Prior Art) Saturated linear polyester represented by polyethylene terephthalate has excellent mechanical properties, heat resistance, weather resistance, electrical insulation, chemical resistance, etc.
It is widely used in a wide range of fields such as electrical applications and magnetic tapes. Usually, a polyester film is obtained by melt-extruding polyester and then biaxially stretching it. in this case,
In order to increase the uniformity of film thickness and the casting speed, when the sheet-like material melt-extruded from the extrusion die is rapidly cooled on the surface of the rotary cooling drum, the adhesion between the sheet-like material and the drum surface is increased. There must be. As a method for increasing the adhesion between the sheet-shaped material and the drum surface, a wire-shaped electrode is provided between the extrusion die and the rotating cooling drum to apply a high voltage, and static electricity is deposited on the upper surface of the unsolidified sheet-shaped material. It is known that a method of rapidly cooling the sheet while closely contacting the sheet with the surface of the cooling body (hereinafter referred to as electrostatic adhesion cast method) is effective (for example, Japanese Patent Publication No. 37-6142).

Uniformity of the film thickness is a very important characteristic in the film quality, and since the film productivity directly depends on the casting speed, it is very important to increase the casting speed to improve the productivity. Because,
Great efforts have been made to improve electrostatic adhesion.

It is known that electrostatic adhesion is an effective means for increasing the amount of charges on the surface of the sheet-shaped material. Further, it is known that modifying the polyester raw material used in the film formation of the polyester film is an effective means for increasing the charge amount on the surface of the sheet material in the electrostatic adhesion cast method.

Conventionally, as the modification method, a method of adding an alkali metal compound or an alkaline earth metal compound in the production process of polyester is known. However, it is necessary to add a large amount of metal compound in order to impart a high degree of electrostatic adhesion by this method. There is a problem that the stability of the polyester to which these metal compounds are added decreases. A method of improving stability by using a phosphorus compound in combination has been proposed, but it cannot be said to have reached a satisfactory level.

(Problems to be Solved by the Invention) In view of the above-mentioned circumstances, the inventors of the present invention have earnestly studied a method of imparting a high degree of electrostatic adhesion with a metal compound in the smallest possible amount, and completed the present invention. That is, the present invention is modified by a novel method which has not been known at all, that is, the effect of imparting electrostatic adhesion by a metal compound is enhanced by changing the structure of the polyester substrate itself, and the addition amount of the metal compound is reduced. It is an object of the present invention to provide a method for forming a high-quality polyester film having excellent thickness uniformity from a polyester composition as a raw material at a high speed.

(Means for Solving the Problems) In the present invention, the polyalkylene glycol and / or its derivative is 0.1 to 10% by weight, and the alkali metal salt derivative of sulfonic acid is an alkali metal to form 0.0003 to
This is a method for producing a polyester film in which a polyester composition containing 0.1% by weight is melt-extruded into a film shape, and then the melt-extruded film is electrostatically adhered to a rotating cooling roll to be rapidly cooled and solidified.

A preferred embodiment of the present invention is the method for producing a polyester film according to the present invention, wherein the polyester film is further stretched 1.1 times or more in at least one direction.

The polyester of the present invention may be any film-forming polyester obtained from a dibasic acid and a dihydric alcohol or a copolymer thereof. Polyethylene terephthalate and its copolymer are typical examples of the polyester, but the polyester is not limited thereto.

Examples of the polyalkylene glycol used in the present invention include polyethylene glycol, polypropylene glycol, polytetramethylene glycol and copolymers thereof, and polyethylene glycol and copolymers thereof are particularly suitable.

The polyethylene glycol derivative includes an ether type (alkyl group: C _{8 to} C ₉ or C ₁₂ to ₁₈ ) as an alkyl ether type alkyl allyl ether type and an alkyl thioether type, and an ester type (alkyl group: C
_{As 12- C18} ), an alkyl ester type or a sorbitan monoalkyl ester type is preferable.

The molecular weight of the polyalkylene glycol used in the present invention is not particularly limited, but is 200 to 200,000, preferably 300 to 20,000, more preferably 400 to
Those of 6,000 are preferred. If the molecular weight is less than 200, the effect of improving electrostatic adhesion becomes small, and the molecular weight is 2
When it is more than 100,000, the dispersibility in polyester is lowered and coarse projections are formed when the film is formed, which is not preferable. The terminal group is also not limited, and any of those having hydroxyl groups at both ends, those having hydroxyl groups at only one end, and those having both ends blocked with other bonds can be used.
In addition, polyalkylene glycol is one of the glycol components.
It may be added in the form of a solid polyester.

The addition amount of the polyalkylene glycol and / or its derivative is 0.1 to 10% by weight based on the polyester,
It is preferably 0.2 to 5 weight. If it is less than 0.1% by weight, the effect of improving electrostatic adhesion becomes small, which is not preferable.
On the other hand, if it exceeds 10% by weight, the effect of improving electrostatic adhesion is saturated and the heat resistance of the polyester is deteriorated, which is not preferable.

Examples of the alkali metal salt derivative of sulfonic acid used in the present invention include compounds having the following structures.

RSO ₃ Me Here, R is an alkyl group having 1 to 20 carbon atoms, and Me is an alkali metal such as Li, Na, K, or Cs.

As the alkali metal salt derivative of sulfonic acid, an alkali metal salt derivative of sulfonic acid may be directly added to the polyester production process, or a sulfonic acid compound and an alkali metal salt compound may be added to the polyester production process to obtain a polyester production process. The alkali metal salt derivative of the sulfonic acid may be formed therein.

Specific examples of the alkali metal salt derivative of sulfonic acid include sodium methanesulfonate, potassium methanesulfonate, sodium ethanesulfonate, lithium benzenesulfonate, sodium benzenesulfonate, potassium benzenesulfonate, lithium p-toluenesulfonate,
sodium p-toluene sulfonate, sodium m-toluene sulfonate, sodium o-toluene sulfonate, sodium p-ethylbenzene sulfonate, sodium dodecyl benzene sulfonate, potassium dodecyl benzene sulfonate, potassium octadecyl benzene sulfonate, 2-naphthalene sulfone Sodium acid salt, sodium octadecylbenzene acid, potassium 2-naphthalenesulfonic acid, etc. may be mentioned. Among these compounds, the sodium salt or potassium salt of aromatic sulfonic acid is particularly preferable.

When an alkali metal salt derivative of sulfonic acid is formed in the polyester production step, the sulfonic acid forming the alkali metal salt derivative of sulfonic acid and the alkali metal compound may be added to the polymerization step. The sulfonic acid may be added in the acid form or in the ester form. Examples of the alkali metal compound include fatty acid salts of alkali metals, alkoxides of aromatic carboxylates, glycosides, oxides and hydroxides. The sulfonic acid compound is preferably used in the acid form, and the alkali metal compound is preferably used as a lower fatty acid salt.

Only when the alkali salt derivative of sulfonic acid is used, the combined effect of polyalkylene glycol for improving electrostatic adhesion is exhibited. Even if the metal salt of sulfonic acid is a metal salt other than alkali metal, the combined effect is not exhibited. In addition, even if it is an alkali metal salt, the effect of combined use is not exhibited with salts of acids other than sulfonic acid derivatives. For example, even if it is a salt of sulfuric acid or alkyl sulfuric acid, the combined effect is not exhibited. Further, the combined effect is not exhibited even in the case of a system comprising an alkali metal compound or an alkaline earth metal compound and a phosphorus compound which has been known as an additive system for improving electrostatic adhesion. In systems other than the method of the present invention, the combined use of polyalkylene glycol rather acts to reduce electrostatic adhesion.

The addition amount of the alkali metal salt derivative of sulfonic acid is 0.0003 to 0.
1% by weight, preferably 0.001 to 0.05% by weight, more preferably 0.002 to 0.02% by weight is suitable. If it is less than 0.0003% by weight, the effect of improving the electrostatic adhesion becomes small, and if it exceeds 0.1% by weight, the effect of improving the electrostatic adhesion is saturated and the heat resistance of the polyester is deteriorated. Is not preferred.

The addition of the component forming the polyalkylene glycol or the sulfonic acid alkali metal salt derivative or the sulfonic acid alkali metal salt derivative can be appropriately selected at any stage in the polymerization process. The component for forming the alkali metal salt derivative of the acid is preferably added before the esterification reaction or the transesterification reaction is started until the intrinsic viscosity of the polyester reaches 0.2.

The polyester composition used in the method of the present invention is not particularly limited as long as it satisfies the above conditions. For example, a polyester produced by a transesterification method or a polyester produced by a direct polymerization method may be used. Good. As the transesterification catalyst and polycondensation catalyst for producing polyester, a conventionally known catalyst can be appropriately selected and used. Further, addition of various additives in order to suppress side reactions during the production of polyester or to improve the stability of polyester is not limited at all.
Further, a batch type polyester may be used, or a continuous type polyester may be used.
Further, it may contain a lubricant composed of inorganic or organic fine particles, or may contain so-called internal particles which are precipitated in the polyester production step if the above requirements are satisfied.

In the method of the present invention, there is no limitation on the structure of the electrostatic application device and the electrostatic application conditions, and it may be set arbitrarily. For example, as the structure of the electrostatic application device, the electrode structure, the presence or absence of a counter electrode, the positional relationship between the electrode or the counter electrode and the extrusion port or the cooling roll,
As the electrostatic application condition, the set voltage and the current value may be set arbitrarily.

The film in the method of the present invention may be an unstretched film, a uniaxially stretched film or a biaxially stretched film, but is 1.1 times or more in at least one direction, preferably 2.
Stretching 5 times or more is preferable in order to improve mechanical properties and other physical properties and to provide various uses.

(Example) Next, the Example and comparative example of this invention are shown. All parts in the examples mean parts by weight unless otherwise specified. The measuring method used is shown below.

(1) Intrinsic viscosity The polymer is dissolved in a mixed solvent of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measured at 30 ° C.

(2) Electrostatic adhesion An electrode made of tungsten wire is provided between the die of the extruder and the cooling drum, and a voltage of 10 to 15 KV is applied between the electrode and the casting drum to perform casting. The surface of the raw material of the casting is visually observed and evaluated by the casting speed at which pinner bubbles start to occur. The higher the casting speed, the better the electrostatic adhesion.

(3) Thickness unevenness in the longitudinal direction The film thickness was measured for a film length of 10 m with a contact type continuous thickness meter, and the thickness unevenness was calculated by the following formula.

Example 1 519 parts of terephthalic acid, ethylene glycol (EG) 4
31 parts of triethylamine and 0.16 parts of triethylamine were charged into a stainless steel autoclave equipped with a stirrer, a distillation column and a pressure regulator, pressurized with nitrogen and maintained at a gauge pressure of 2.5 kg / cm, and water produced at 240 ° C. was distilled. The esterification reaction was carried out while continuously removing it from the top of the tower. 1 after starting the reaction
After 20 minutes, the pressure was released to obtain a product having an esterification rate of 98%. To this esterified product, 31.5 parts of polyethylene glycol having a molecular weight of 2000 was added, and the mixture was stirred at normal pressure for 24 hours.
The mixture was stirred at 0 ° C. for 10 minutes, and 0.25 part of sodium p-toluenesulfonate (50 ppm in terms of Na atom based on the produced polyester) was dissolved in 10 parts by volume of EG and the average particle size was 0.7 μm. A dispersion of 1.2 parts of kaolinite dispersed in 8 parts by volume of EG was added, and the pressure was 240 ° C. at normal pressure.
After further stirring for 10 minutes at 240 ° C., it was transferred to a polycondensation reactor at a temperature of 240 ° C., and the pressure of the reaction system was gradually reduced to 0.05 mmHg while raising the temperature to 275 ° C. over 45 minutes.
The polycondensation reaction is carried out at the same pressure for about 85 minutes to give an intrinsic viscosity of
630 polymer was obtained. The electrostatic adhesion of the obtained polymer was 65 m / min, which was extremely good.

In addition, when a film was formed using the above raw materials under the following conditions, 2
Even when the film was formed at a take-up speed of 20 m / min, the film surface was free from defects and a high-quality film having a vertical thickness unevenness of 6.5% or less was obtained.

Film forming conditions Film thickness: 12 μ (after biaxial stretching) Extrusion temperature: 290 ° C. Electrostatic adhesion conditions: 0.25 mmφ SUS electrode, applied voltage 10
-15 KV Longitudinal stretching ratio: 3.5 times Longitudinal stretching temperature: 90 ° C Horizontal stretching ratio: 3.5 times Horizontal stretching temperature: 130 ° C Heat set temperature: 222 ° C Comparative Example 1 Addition of polyethylene glycol by the method of Example 1. A polyester was obtained by the same method as in Example 1 except that the polyester was stopped. The electrostatic adhesion of the obtained polyester was 15 m / min. Further, the polyester was used to form a film under the same conditions as in Example 1, but in order to obtain a high quality film as obtained in Example 1, the film could be formed only at a take-up speed of 50 m / min or less. It was

Comparative Example 2 A polyester was obtained by the same method as in Example 1 except that the addition of sodium p-toluenesulfonate was stopped by the method of Example 1. The electrostatic adhesion of the obtained polyester was 15 m / min. The polyester was used to form a film under the same conditions as in Example 1, but in order to obtain a high quality film as obtained in Example 1, the film could only be formed at a take-up speed of 50 m / min or less. .

Comparative Examples 3 to 6 Instead of sodium p-toluenesulfonate in the method of Example 1, sodium lauryl sulfate, sodium sulfate, sodium acetate and sodium bromide were used (addition amount of any compound was based on the produced polyester). Polyester was obtained by the same method as in Example 1 except that the amount of Na was 50 ppm. The electrostatic adhesion of the obtained polyester was 10 to 15 m / min. A film was formed using the polyester under the same conditions as in Example 1, but in order to obtain a high-quality film as obtained in Example 1, film formation was possible only at a take-up speed of 50 m / min or less, and It was

Examples 2 to 8 Electrostatic adhesion of polyesters produced by changing the kind and addition amount of the alkali metal salt derivative of polyalkylene glycol and / or sulfonic acid according to the method of Example 1 and Example 1 using the polyesters. Table 1 shows the maximum film forming rate when the film was formed under the same conditions. It can be seen that in each of the examples, a high quality film can be formed at a high take-up speed.

Example 9 Polyethylene glycol having a molecular weight of 1000 (31.5 times) was added to the esterified product esterified by the method of Example 1, and the mixture was stirred at normal pressure and 240 ° C. for 5 minutes to give 0.107 parts of sodium acetate. (50 ppm in terms of Na atom) was added as a solution dissolved in EG, and the mixture was stirred at 240 ° C. under normal pressure for 5 minutes, and then 0.248 parts of p-toluenesulfonic acid monohydrate was dissolved in EG. After adding and stirring at atmospheric pressure and 240 ° C. for 5 minutes, 1.2 parts of kaolinite having an average particle size of 0.7μ is added as a dispersion liquid in EG and stirred at atmospheric pressure and 240 ° C. for 10 minutes. After that, it was transferred to a polycondensation reactor at 240 ° C.
The polycondensation reaction is carried out in the same manner as described above, and the intrinsic viscosity is 0.632.
Of polyester was obtained. The electrostatic adhesion of the obtained polyester was 67 m / min. When a film was formed using the polyester as a raw material under the same conditions as in Example 1, 230
Even when the film was formed at a take-up speed of m / min, there was no defect on the film surface, and a high-quality film having a thickness variation in the longitudinal direction of 6.5% or less was obtained.

Comparative Example 7 A polyester was obtained by the same method as in Example 9 except that polyethylene glycol was not added by the method of Example 9. The electrostatic adhesion of the obtained polyester was 15 m / min. The polyester was used to form a film in the same manner as in Example 9, but in order to obtain a high quality film as obtained in Example 9, the film could only be formed at a take-up speed of 50 m / min or less.

Comparative Example 8 A polyester was obtained by the same method as in Example 9 except that sodium acetate was not added by the method of Example 9. The electrostatic adhesion of the obtained polyester was 15 m / min. Further, a film was formed by using the polyester in the same manner as in Example 9, but in order to obtain a high quality film as obtained in Example 9, 50
The film could only be formed at a take-up speed of m / min or less.

(Effect of the Invention) When a polyester film is produced by the method of the present invention, there is an effect that a polyester film having excellent thickness uniformity can be formed into a film at a high speed.

Claims (2)

[Claims] 1. A polyalkylene glycol and / or its derivative in an amount of 0.1 to 10% by weight and an alkali metal salt derivative of sulfonic acid as an alkali metal in an amount of 0.0003.
A method for producing a polyester film, which comprises melt-extruding a polyester composition containing 0.1 to 0.1% by weight into a film shape, then electrostatically adhering the melt-extruded film electrostatically to a rotating cooling roll and rapidly solidifying. 2. A method for producing a polyester film, wherein the polyester film according to claim 1 is stretched 1.1 times or more in at least one direction.