JPS59229314A - Polyester film - Google Patents

Abstract

PURPOSE:To improve the accuracy of film thickness by a method in which a polyester film is produced by using the process of electrostatically impressed cooling, and the specified amount of a specified metallic compound is added to the polyester at the process before extruding at molten state. CONSTITUTION:A polyester film is produced by using the process of electrostatic impressed cooling, and 0.01-1wt% metallic salt of monocalboxylic acid or dicalboxylic acid of aliphatic series having 70-290 deg.C melting point, is added to the polyester at the process before extruding at molten state, thereby manufacturing the polyester. By doing so, even for the polyester to which the process of electrostatic impressed cooling is not able to be applied effectively due to the high specific resistance at molten state as it is, the process of electrostatic impressed cooling may be used without deteriorating heat resistance, transparency and color tone, and the accuracy of the film thickness may be improved to a preferable degree.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a polyester film having excellent thickness accuracy.

More specifically, the thickness accuracy is improved by modifying the conductivity of the raw material polyester.

Conventional technology Biaxially oriented polyester films, especially polyethylene terephthalate, have excellent mechanical properties, electrical properties, chemical resistance, and one-dimensional stability, so they are used for magnetic tapes, capacitors, packaging, and plate making. It is used as a base material in many fields, such as for electrical appliances, electrical disconnection, and photographic film.

Incidentally, in recent years, the required characteristics for film quality have become increasingly strict, and in particular, reducing long-term ridges of the film, that is, improving thickness accuracy, has become an indispensable condition.

For this purpose, 1. For example, when a sheet material melted and extruded from an extrusion die is rapidly cooled in a rotating cooling drum as described in Japanese Patent Publication No. 32-196/Gu, an electrostatic charge is generated on the surface of the sheet material. A so-called electrostatic cooling method is known in which the sheet material is brought into close contact with a cooling surface.

However, in this electrostatic application cooling method, when the speed of the rotating cooling drum is increased for the purpose of increasing productivity, the adhesion between the sheet material and the cooling drum decreases, resulting in the formation of so-called bound bubbles. The quality characteristics required for the product are unacceptable.

These bound bubbles are partly due to the high specific resistance of the raw polyester when melted.For example, the value measured by the method described below is particularly high! When the value exceeds x/θaΩ-b, 1 is likely to occur, making it difficult to efficiently obtain a high-quality film.

One way to improve this drawback is, for example, by Tokkai Sho!
/-2θko4? As described in the above publication, a method is known in which a metal compound is added or contained during the production of polyester to reduce the specific resistance during melting.

However, according to the knowledge of the present inventors.

If such a method is used to reduce the specific resistance during melting, it is necessary to ensure the effect during the production of polyester, since the formation of a large amount of the metal compound lengellicol bonds is promoted, and during the production of thermally stable chill. Over a long period of time, some or all of the polyester oligomer may precipitate as metal salts or other forms of metal salts, giving rise to fine particles insoluble in the polyester.

If fine particles insoluble in the polyester are produced, the transparency, surface roughness, slipperiness, etc. of the film may change, and the desired film may not be obtained.

By the way, depending on the use of the polyester film, it is often necessary to avoid adding these metal compounds at the polyester manufacturing stage in order to maintain its transparency and slipperiness within a certain range. If the resistivity during melting is high, the electrostatic cooling method cannot be used effectively. We are actively investigating ways to modify polyester, which has high resistivity and cannot be effectively applied to the electrostatic cooling method as it is. As a result, heat resistance was improved by adding a specific amount of a specific metal compound to the polyester.

The inventors have discovered that it is possible to improve the thickness accuracy of a film to a desirable extent by using an electrostatic cooling method without impairing transparency and color tone, and have arrived at the present invention.

That is, 1 the present invention is a polyester film produced using an electrostatic application cooling method, in which an aliphatic monocarboxylic acid or dicarboxylic acid having a melting point of 2θ to -20°C is added to the polyester in a process before the melt extrusion process. Metal salt is 0.07-7
% by weight of the polyester film.

The present invention will be explained in more detail below.

The polyester film referred to in the present invention is made of polyester containing ethylene terephthalate units of tθ mol or more [
It refers to a film that has been processed by m.

The raw material polyester may be a polyester produced by any method. For example, esterification or transesterification of a dibasic acid whose main component is terephthalic acid or its lower alkyl ester and a glycol whose main component is ethylene glycol. It is obtained by performing a polycondensation reaction after the reaction.

In this case, the specific resistance during melting of the resulting polyester varies over a wide range depending on the type and amount of the catalyst, the type and amount of the phosphorus compound added as an auxiliary agent, etc., but among these, the specific resistance during melting! If the value is as high as ×/θ6Ω-m or more, the electrostatic application cooling method can be utilized.

The gist of the present invention is to reduce the specific resistance during melting by adding a specific amount of a certain metal compound to polyester, which has a high specific resistance when melted, before the melt extrusion process, but in this case, the added metal compound has a high melting point. It needs to be a metal salt of an aliphatic monocarboxylic acid or dicarboxylic acid of 2Q~290°C.

Specifically, metal salts of aliphatic monocarboxylic acids or dicarboxylic acids having about 4t to 30 carbon atoms, especially lithium salts, sodium salts, potassium salts, magnesium salts, manganese salts, zinc salts, calcium salts, aluminum salts, etc. Mention may be made of one type of selected compound, V-soil. The effects of the present invention are effectively exhibited in the case of magnesium salts, manganese salts, zinc salts and calcium salts. These metal compounds are generally compatible with polyester and rarely deteriorate the transparency and thermal stability of the resulting film.

Note that all of these pure compounds used in the present invention have a melting point of 2θ
~,? Must be 90°C.

This is because if the melting point is less than 2θ°C, the film will be exposed to high temperatures for a short period of time during the melt extrusion process, which will easily cause decomposition or deterioration, which will have an adverse effect on the film. Furthermore, the films tend to adhere to each other, resulting in poor handling efficiency.

On the other hand, if the melting point of the metal compound exceeds 0° C., it will not melt at all or will not melt sufficiently during the melt extrusion process, so that the original purpose of improving the electrical conductivity of polyester will not be fully achieved.

Namely, 5. According to the knowledge of the present inventors, there is a method for reducing the specific resistance of polyester during melting and improving the adhesion between the molten sheet material and the cooling body.

It is not sufficient to simply add a metal compound to the polyester, and it is preferable that the metal compound be able to move freely in the molten cypolymer during molding into a molten sheet.

Examples of metal compounds that can be used in the present invention that meet these requirements include magnesium valmitate, manganese valmitate, zinc valmitate, magnesium stearate, zinc stearate, potassium oleate, sodium oleate, and oleic acid. Examples include, but are not limited to, magnesium, zinc oleate, magnesium sebacate, manganese sebacate, and the like.

The amount of these metal compounds added varies depending on the type of additive, but is 0.1 to 7% by weight based on the polyester.
Preferably θ, θ! ~θ,! Heavy I-CH is preferred. When the amount added is less than 0.0/wt-h, it is difficult to achieve the desired reduction in the specific resistance of the polymer when melted, and when the amount added exceeds 7 wt%, thermal stability often deteriorates. As a result of decomposition or deterioration, air bubbles or vertical streaks may appear in the film, and transparency and color tone may be impaired.

In the present invention, it is necessary to mix these metal compounds with the 1M polyester which has undergone a reaction before the melt extrusion process. It is usually best to add these metal compound powders before or during the drying process to make the powder as uniform as possible.

Note that in the present invention, after forming an amorphous sheet-like material using the electrostatic cooling method, a normal stretching process can be used.

That is, sequential biaxial stretching or simultaneous biaxial stretching in the longitudinal and transverse directions/6
A method such as heat treatment at 0° C. to 2’10° C. (for example, the method disclosed in Japanese Patent Publication No. 30-1973) can be used.

8- Effects of the Invention As detailed above, according to the present invention, it is possible to add a specific amount of a specific metal compound to polyester, which cannot be effectively applied to the electrostatic cooling method as it is because of its high specific resistance when melted. Good heat resistance.

The thickness accuracy of the film can be improved to a desirable degree using the electrostatic cooling method without impairing transparency and color tone, and its industrial value is great.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples and Comparative Examples.

In addition, "parts" in Examples and Comparative Examples indicate "parts by weight." The measurement method used is shown below.

/)Measurement of resistivity during melting of polyester
1t, J, Appl, Phys, ) Volume 1, Volume 1/Li? ~//! I followed the method described on page 36 of this paper. However, in this case, the temperature at the time of melting the polymer composition is 29θ°C, and the direct current is 3. The value immediately after applying θθOV is taken as the specific resistance at the time of melting.

2) Thickness unevenness of polyester film The film thickness is measured at 10 points every 70 points in the width direction, for a total of 700 points at each of 10 points every 7000 m in the longitudinal direction of the film.

The film thickness was measured using a micrometer manufactured by Anritsu Denshi, and the measurement was made by stacking 10 films around the relevant location and converting the thickness to 1/sheet.

The maximum value of all measured values is Xmax, the minimum value is X
min, ICXzXmin when the arithmetic mean value is
is the thickness unevenness of the film, and this value is preferably 0.73 or less.

3) Film haze It was measured using a turbidity meter NDH-, model 2A manufactured by Nippon Muriroki, according to the method of ASTM D10θj-, .

4t) Color tone of the film The b value, which is an index of the yellowness of the film, was measured using a photoelectric color difference meter (To-yori type) manufactured by Tokyo Denshoku. The larger the b value, the stronger the yellowish tinge.

Polyester film (methanol/hydroxide) IJ
The amount of diethylene glycol contained in the sample was determined by gas chromatography and expressed in terms of mole ratio relative to ethylene glycol. If the number of diethylene glycol bonds increases, the melting point of the polymer will decrease and the heat resistance will deteriorate, so the smaller the amount, the better.

Example/ 700 parts of bis-β-(hydroxyethyl) terephthalate oligomer was placed in an esterification reaction tank equipped with a stirring device, and 2 parts of terephthalic acid and a part of ethylene glycol were added to form an ester at 210°C under atmospheric pressure. A chemical reaction was carried out. After a period of time, a polyester oligomer with an esterification reaction rate of 2% was obtained.

Next, /θd part of this reaction mixture (from now on, n10
Polyester of θ part is obtained. ) was taken, and 2g of lithium fluoride was added to the average particle size of 3μ while keeping it at θ°C.
part and 0.02 part of phosphoric acid were added.

Next, 0003 parts of J antimony trioxide was added and polymerization was carried out according to a conventional method. That is, after the addition of antimony trioxide, the temperature in the system was brought to 2rj°C and the pressure was brought to /Ht in 10 minutes, and thereafter the pressure was gradually reduced to give the final KO, J11*Hy. After an hour, the reaction was stopped and a polyester having an intrinsic viscosity of 0.66 was obtained.

The specific resistance of polyester when melted is y×l0IlΩ
-It was a hireling.

Next, 0.01 part of magnesium stearate was added to 100 parts of the obtained chip-shaped polyester, and the mixture was mixed uniformly with pre-mixture and dried.

The specific resistance of this polyester composition when melted was measured to be 12 x 10'' Ω.

-Then, this polyester composition was mixed with 2? The mixture was extruded into a sheet using an extruder at θ° C., and an amorphous sheet was obtained using an electrostatic cooling method. The conditions for applying static electricity at this time are as follows. That is, a tungsten wire with a diameter of θ is used as a positive electrode, and is stretched on the upper surface of a rotating cooling drum in a direction perpendicular to the flow of the sheet.
V was applied.

After obtaining the amorphous sheet, 3. θ times, 3 horizontally
．． Stretched 1x, always thickness/! The extrusion rate and the speed of the rotary cooling body were adjusted so as to obtain a biaxially stretched film of μ. At this time, the relationship between the speed of the rotary cooling body, bound bubbles, and thickness unevenness of the obtained film was observed. .

The speed of the rotary cooling body was gradually increased from -2OfFi 7 minutes, but no bound bubbles were generated even at +10 fn 7 minutes, and the thickness unevenness of the biaxially stretched film obtained at this time was 0.
．． Table 70 was small and sufficiently satisfactory.

Table 7 also shows the amount of diethylene glycol, transparency, and color tone, which are indicators of the heat resistance of the obtained film, along with other results.
As shown in Figure 2, it was at a level that caused no practical problems.

Comparative Example/Example/The film-forming raw material polyester was used in the same manner as Example/, except that polyester to which no magnesium stearate was added was used to obtain a thickness of /! A μ polyester film was obtained.

When the rotating cooling body speed reached 32 m/min, trapped bubbles were observed, but the speed was further increased to 7 min. The thickness unevenness of the film obtained at this time was extremely poor as θ and j j.

Examples - In Example//, magnesium stearate was used.

The results at this time are shown in Table/.

Comparative Example Magnesium costearate was added at the time of polyester production. That is, after adding phosphoric acid in Example//, magnesium stearate θ, θ! M condensation reaction was conducted in the same manner as in Example except that

The obtained polyester has an intrinsic viscosity θ, /! −/, diethylene glycol content”,! Morchi, and its color tone is b
The value is 2/, making it an extremely yellowish polyester! ! !
It was not worth the membrane.

In an example, 10 parts of dimethyl terephthalate, 6 parts of ethylene glycol, and 0.7.2 parts of calcium acetate hydrate were placed in a reactor, heated and raised, and methanol was distilled off to carry out a transesterification reaction.

Triethyl phosphite 0.0 after completion of transesterification reaction
After adding a solution of 0.71 parts of triethyl phosphate and 0.71 parts of triethyl phosphate, and further adding parts of antimony trioxide θ, O4, polymerization was carried out according to a conventional method to obtain a polyester.

A large number of uniform, fine precipitated particles were formed in the polyester, and the particle size was approximately 15 μm.

The specific resistance of this polyester when melted is 8! ×/θ9Ω-m
Met.

Next, 0.20 parts of calcium stearate was added to 700 parts of this polyester, and a polyester film was obtained using the electrostatic cooling method in the same manner as in Example.

The results are shown in Table 1, and the polyester film obtained was excellent in all of its high-speed spreadability, thickness unevenness, heat resistance, transparency, and color tone.

Comparative Example 3 In Example d, calcium stearate was added at the time of polyester production. That is.

A polycondensation reaction was carried out in the same manner as in the example except that 20 parts of calcium stearate θ was added after the transesterification reaction.

A large number of precipitated particles were observed in the obtained polyester, but their morphology was different from that of Example 6. That is, the central portions 16- of the precipitated particles aggregated with each other to form coarse particles.

Therefore, it was necessary to form a film using a polyester composition different from that originally intended.

Claims (1)

[Claims] (1) A polyester film produced using an electrostatic application cooling method, which is a metal salt of an aliphatic monocarboxylic acid or dicarboxylic acid having a melting point of 2θ to λ and 0°C relative to the polyester in a process before the melt extrusion process. A polyester film containing 0.0/~/wt% of