KR890000038B1 - Preparation of polyester film - Google Patents

Abstract

A method for polyester film comprises (i) condense-polymg. at least 90 mol.% of ethyleneterephthalate with alk. metal 5-sulfoisophthalate 0.1-5.0 mo.% and glycole to produce polyester having sp. resistance 1X10 power 7 to 5X10 power 8 ohm.cm, (ii) melt-extruding prepg. polyester to obtain polyester sheets, (iii) giving static charge on the upper surface of sheets, and (iv) dual axis drawing.

Description

Manufacturing method of polyester film

1 is a graph showing the relationship between the polymer resistivity and the rotational cooling drum speed, that is, the resistivity and the adhesion at 285 ° C., which is a measure of the polymer conductivity of the present invention. To hold the drum speed as an indirect measure of adhesion)

2 is an electrostatic application device of the present invention.

3 is a resistivity measuring apparatus of the present invention.

* Explanation of symbols for main parts of the drawings

In FIG. 2

1 electrode 2 DC high voltage generator

3: chucking dung 4: T-die

5: sheet

In FIG.

1: DC high voltage generator 2: Current 켸

3: high pressure meter 4: heating element

5: measuring polymer 6: tubular electrode

The present invention is to produce a film having a uniform thickness in the advancing direction and the transverse direction of the sheet by increasing the conductivity in the production of the film by a polyester polymer of a constant composition ratio, while increasing the adhesion to the casting drum It is about a method.

In general, when the original molten polymer sheet is cooled and solidified on a rotating casting cooling drum surface with thermoplastic resin, a wire or knife electrode is installed in parallel with the upper surface of the horizontal line where the sheet starts to contact the casting cooling drum surface. The crystallinity is low and low by a conventional electrostatic application method in which a DC or an alternating current of more than a few kilovolts is applied to the electrode and the sheet has a positive or negative charge on the upper surface thereof, thereby cooling and solidifying the sheet in close contact with the casting cooling drum surface. It was possible to obtain a sheet with uniformity and low width fluctuation.

However, in the above-mentioned electrostatic applied film forming method, if the film forming speed is increased to increase the productivity during film forming, the rotation speed of the casting cooling drum should be relatively high, and thus the amount of charge on the surface of the sheet-like material adhered to the surface of the rotating casting cooling drum. Since the adhesion is relatively small, the adhesion between the sheet and the cooling drum surface is weakened, resulting in poor thickness uniformity of the film forming film. As a result, pinholes are generated on the film surface, resulting in deterioration of quality.

To solve this problem, if the voltage applied to the electrode placed between the extrusion block and the cooling drum surface is increased to have a large amount of electrostatic charge on the surface of the sheet-like material, an arc discharge occurs between the electrode and the cooling drum surface and the cooling drum surface This erodes and eventually becomes unusable. Therefore, it is virtually impossible to increase the voltage applied to the electrode to some extent by the conventional electrostatic application method.

In addition, in the case of forming a thin film on the surface of a cooling drum to form a thin film for forming a thin film, the sheet is likely to be damaged by discharge from an electrode. Therefore, if the film is formed by the electrostatic application method by lowering the voltage applied to the electrode, the adhesion between the sheet-like material and the cooling drum surface is bad. Therefore, high-quality film production is possible only by reducing the rotational stone degree of the cooling drum to ensure good adhesion. Mass production was impossible.

The present invention improves the problems of the conventional method, and the adhesion between the polymer sheet and the cooling drum when the polyester film is formed using the electrostatic application method is applied voltage, electrode position, rotational speed of the cooling drum, thickness of the polymer sheet, polymer type Although it is influenced by factors such as degree, degree, temperature, and electrode diameter, it has been found that the conductivity of the polymer has a significant lower effect on the adhesion.

Such a fact could solve the problems of the conventional method and will be referred to as a basic technical idea that led to the present invention. That is, based on the fact that the conductivity of the polymer significantly affects the adhesion, the conductivity of the polymer can be adjusted appropriately, thereby making it possible to speed up the circumference of the cooling rotating drum and to produce the film at high speed. In other words, by modifying the polyester raw material used to lower its electrical resistivity, it is possible to solve the problems of the conventional method to increase the productivity and at the same time to produce a high-quality polyester film with no defects on the film surface and uniform thickness can do.

In particular, in the present invention, in order to reduce the electrical resistivity, the reaction composition ratio of the polymer must be controlled to form a film with high efficiency as the polymer having a low Hamper resistivity. Specifically, at least 90 mol% of the structural units of the polyester production composition are made of ethylene terephthalate, and 0.1-5 mol% is made of 5-alkali metal sulfoisophthalate to obtain a specific resistance of l × 10 ^7. After melt extrusion of polyester with a size of -5 × 10 ⁸ Ωcm into a sheet form, electrostatic charge is applied to the upper surface of the sheet-like material rule, and when it is electrostatically adhered to the surface of the rotating cooling drum, it is cooled and solidified. It is a manufacturing method of the polyester film characterized by the above-mentioned.

The polyester copolymers used in the present invention described above are at least 0.1-5 mole% of 5-sulfoisophthalic acid alkali metal salts or ester derivatives thereof, such as 5-lilium sulfoisophthalic acid and 5-sodium sulfoisophthalic acid. , 5-potassium sulfoisophthalic acid, 3,5-bis (epoxycarbonyl), sodium benzene sulfonate, 3,5-bis (epoxycarbonyl) benzenesulfonate potassium, 5-bis (β-hydroxyepoxycarbonyl) Lithium benzenesulfonate, 3,5-bis (β-hydroxyepoxycarbonyl) sodium sulfonate, 3,5-bis (β-hydroxyepoxycarbonyl) benzenesulfonate potassium, etc. When the total amount of alkali metal phthalate salts or ester derivatives thereof is less than 0 · l mol%, the specific resistance of the molten polymer becomes 10 ⁹ Ωcm or more, which does not exhibit the effect of the present invention, and when it is 5 mol% or more, the mechanical strength of the polyester film is lowered. And manufacturing costs rise It is not straight.

The dicarboxylic acid component used as a raw material of ethylene terephthalate having a reaction composition ratio of 90 mol% or more is mainly composed of terephthalic acid or diethyl terephthalate, but a part of the acid component isophthalic acid, diphenyldicarboxylic acid, P- It may be substituted with β-hydroxyepoxy benzoic acid, adipic acid, carboxylic acid of sebacic acid or ester derivatives thereof.

The glycol component is mainly composed of ethylene glycol or ethylene oxide, but some of them are alkylene glycols having 3 to 10 carbon atoms, 1,4 bis (β-hydroxyepoxy) benzene, bisphenol A, and poly inorganic alkyl. You may substitute by glycol, such as len glycol.

In the present invention, oxides, acetates, hydrides and the like of alkali metals or alkaline earth metals are used as the transesterification or esterification catalysts. Specifically, for example, calcium acetate, sodium acetate, lithium acetate, lithium chloride, calcium chloride, sodium chloride, and oxidation Calcium and the like.

Phosphoric acid, phosphorous acid and derivatives thereof are used as the stabilizer. For example, phosphoric acid, phosphorous acid trimethyl phosphate, trimethyl phosphite, triphenyl phosphate, triphenyl phosphite and the like are used, and at least one of them is used. In addition, as means for neutralizing the surface activity of the film, inert fine particles such as calcium carbonate terephthalate, clay, and silica may be added, or internal particles using alkali or alkali metal compounds, phosphorus compounds, and epylene terephthalate used as catalysts may be used. It may be used as a lubricant.

Through the contents described so far, the polyester film manufacturing method according to the present invention is known to be more efficient than the conventional method and also in terms of quality of the film. It becomes clearer.

(Experimental item)

1. Cross-link viscosity of polymer: Value measured at 25 ° C with ortho chlorophenol as solvent

2. Resistivity of polymer: resistivity at 285 ℃ and 3000V voltage measured by the apparatus of FIG.

3. Surface defects: visually judged

A: No defect on the film surface

B: Pinhole defect partially on film surface

C: There is a pinhole defect on the front surface of the pen

4. Film thickness difference

(Production Conditions)

1.Film thickness: 12μ (biaxially stretched)

2. Extrusion temperature: 285 ℃

3. Capacitance casting: Use the tungsten wire of 0.1mm ψ and apply the electrostatic discharge using DC high voltage generator, but apply voltage 3-15KV.

4. Casting drum temperature: 30 ℃ 8. Longitudinal stretching temperature: 110 ℃

5. Longitudinal draw ratio: 33 times 9. Heat treatment temperature: 220 ℃

6. Specimen stretching temperature: 90 ° C l0. Heat Treatment Morbidity: 4%

7. Lateral draw ratio: 3.3 times

Example 1

Stainless steel container with 2,000 parts of diethyl terephthalate, 3.5 parts of 5-sodium sulfoisophthalic acid diethyl ester (1.5%), 1200 parts of ethylene glycol, 0.8 parts of antimony trioxide, and 1.4 parts of calcium acetate After the reaction was completed, the resultant reaction was carried out for 5 hours while continuously removing the methanol produced by heating, and after completion of the reaction, 1.8 parts of triethyl phosphate was added thereto, followed by stirring, which was transferred to a stainless polycondensation reactor. It is then stepped down while stirring. In 1 hour, the temperature was raised to 285 ° C. and polycondensation was carried out for 3 hours and 20 minutes under a vacuum of 1 mmHg or less to obtain a polymer having an extreme degree of 0610. The specific resistance thereof was 2 × 10 ⁷ μm. The thickness difference of the film dried by the conventional method and manufactured by the above-mentioned film forming conditions was very good at ± 1.5%, and there was no surface defect generated in the system by the high speed electrostatic application method.

Example 2

As a comparative example of Example (1), the polymerization was carried out in the same manner as in Example (1) without treatment of 5-sodium sulfoisophthalic acid dimethyl ester to obtain a polymer having a localized viscosity of 0612, wherein the specific resistance thereof was 4 x 10 9 cm 3. By commercial law. The thickness difference of the film dried and manufactured under the same film forming conditions as in Example (1) was not uniform as ± 4%, and many surface defects appeared in the system by the high-speed electrostatic application method.

In addition, the results of the surface defects in Example (1) (2) are shown as the surface defect grades of the test items stated according to the take-up speed (rotary cooling drum speed).

As described in Examples (l) and (2) above, the effect of the present method is low in resistivity, excellent in vibration damping properties, and a film thickness having a uniform thickness due to a small thickness difference between the films. It can be said that a method for producing a good quality film.

Claims (1)

0.1-5.0 mol% or more of at least 90 mol% of ethylene terephthalate, 5-sulfoisophthalic acid alkali metal salt in the preparation of the stretched polyester film with a composition consisting of terephthaltaxate, glycoll, stabilizer, bulking agent and other additives Polycondensation with components such as glycol Method for producing a stretched polyester film, characterized in that the production by the electrostatic method.

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