JPS6025457B2 - polyethylene terephthalate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transparent biaxially oriented polyethylene terephthalate film that has good film formability and handling properties, and has high resistance to thermal deterioration.

In recent years, polyethylene phthalate film has been used for magnetic tape,
It has come to be widely used in photography, capacitor applications, etc.

However, in the field of products that take full advantage of its brightness and transparency, troubles may occur during the film forming process and high-level film processing process, such as insufficient slippage or deterioration due to heat. There were many things. In other words, if the slippage is poor, it will not be easy to wind or unwind the film, and if the film is used or processed at high temperatures, it will easily deteriorate due to heat, resulting in decreased mechanical strength, discoloration, or decreased transparency. This is because processing work becomes difficult and product value decreases. In fields requiring transparency, the transmittance of light with a wavelength of 55 m〃 is at least 70%, preferably 75 m.
It is desirable to exceed %. The technologies conventionally used to impart slipperiness to films can be roughly divided into A.
A method of adding inert fine particles to the reaction system for polyethylene terephthalate synthesis such as titanium dioxide, talc, kaolinite, calcium carbonate, etc.

B. A method in which part or all of the catalyst, color inhibitor, etc. used during the synthesis of polyethylene terephthalate is precipitated during the reaction process and is present as fine particles. There is.

In addition, although not normally used with polyethylene terephthalate, a method of adding lubricants such as stearic acid and zinc stearate is also known. However, both methods of making the above two types of fine particles exist require technology to control the diameter of the fine particles and the amount added, and in order to improve slipperiness, the particle size must be coarse and a large amount must be present. However, they must accept the disadvantage that their efforts may actually reduce the transparency of the film.

Therefore, even if the above two methods are used, the present inventors have found that even if they use the above two methods, they can achieve good or improved slipping properties in a transparent state.
Furthermore, as a result of intensive investigation into whether it was possible to obtain a polyethylene terephthalate film with good heat resistance by adding some kind of organic compound, the structural formula (herein R
represents an alkyl group).
By biaxially stretching and orienting polyethylene terephthalate mixed with 1 to 5% by weight, preferably 0.3 to 4% by weight, 55
It was discovered that a film having a transmittance of 70% or more for light having a wavelength similar to that of the skin can be made, and the present invention was developed based on this finding.

Polyethylene terephthalate as used in the present invention includes copolymers in which 85% or more of the repeating units are ethylene terephthalate units, and cases in which 15% by weight or less of other polymers are mixed.

As can be seen from the fact that the added organic compound has a high melting point, it hardly evaporates due to decomposition or sublimation during the addition process and film forming process. 2. Bag oriented film is made by melt-extruding polyethylene terephthalate using an extruder at a temperature of at least 260 mm or more, followed by biaxial stretching without unstretched film, but the organic compound has compatibility with polyethylene terephthalate. Since it is added before the polymerization process and/or melt extrusion, it melts and is uniformly dispersed at least in the extruder.

For example, in the case of polyvinyl chloride, heating to 205q0 or higher causes severe decomposition, and it is difficult to uniformly mix the organic compound with a higher melting point than that. Addition amount is 0.1% by weight
, preferably 0. If it is less than 5% by weight, preferably 4% by weight, the effect of improving both slipperiness and heat resistance will be insufficient for the purposes of the polyethylene terephthalate melting caused by the addition. This is desirable because it reduces the degree of polymerization. Lubricants often used in resins other than polyethylene terephthalate, such as stearic acid, zinc stearate, lead stearate, liquid paraffin, stearamide, and olefinic acid amide, have low melting points.
Alternatively, the film may emit smoke or be difficult to handle during the two-wheel stretching or heat treatment process, and it is also difficult to control the amount of bleed after the film is coated, and the film surface may become cloudy over time, resulting in poor appearance. It is practically unusable because the degree of polymerization may be significantly lowered in some cases.

Achievement of the object of the present invention with a polyethylene terephthalate film can only be achieved by biaxially stretching the film and, in some cases, further subjecting it to heat treatment. It should be noted that even if is added, improvement in slipperiness and development of heat resistance cannot be expected at all.

The slipperiness of the film was measured using a slip tester manufactured by Toyo Tester according to the method of ASTM D-189.

The heat resistance was expressed as the bending strength (number of bending cycles) after the film was heat-treated at 240° C. for 1 hour. The measurement method is J
According to ISP8115-63 (measurement temperature was room temperature). 5
The transmittance of light with a wavelength of 5.5 h can be measured using a conventional spectrophotometer. The degree of polymerization of polyethylene terephthalate was determined by the intrinsic viscosity measured at 25° C. in orthochlorophenol. There are no particular limitations on the stretching conditions for the film.
As long as it is biaxially oriented, the usual method can be followed, but the stretching ratio should be 5 or more in the machine direction and 2.5 in the transverse direction.
-4.5 times and the stretching temperature is generally 80 to 170 qo, and preferably 160 to 240 qo if heat treatment is required.

Stretching techniques include simultaneous biaxial stretching, sequential biaxial stretching, a combination thereof, and subsequent re-stretching in the -marginal direction.
This will be explained in more detail below using Examples and Comparative Examples.

Comparative Examples 1 to 3 Example 1 80 parts by weight of terephthalic acid and 42 parts by weight of ethylene glycol were charged into an autoclave, and the mixture was heated for 22 hours without adding any catalyst.
Direct esterification reaction was carried out under pressurized conditions of 0 qo and 1.5 kg/kg.

The distilled water was continuously drained out of the system, and when the reaction rate of the system reached 50%, the pressure inside the system started to be released, and finally the pressure was reduced to 245 qo, and the esterification reaction started. has ended. Next, dry process silicon oxide was dispersed in a mixed solution of ethylene glycol and water to form a slurry, and tetraethylammonium hydroxide was added to adjust the bait, and the slurry was added to the transesterification reaction product. Furthermore, 0.06 parts by weight of magnesium acetate tetrahydrate, 0.06 parts by weight of magnesium acetate tetrahydrate, and 0.06 parts by weight of magnesium acetate tetrahydrate.
After adding 0 part by weight of milk and 0.025 part by weight of trimethyl phosphate, military condensation was carried out by a conventional method to obtain polyethylene terephthalate (intrinsic viscosity 0.625) containing 0.07% silicon oxide. This polyethylene terephthalate was crushed and blended with 2% of each organic compound having the following chemical structure (melting point: 230°C), then a stretched film was made by melt extrusion at 280°C, and then one bag was made by 9 pi○. After stretching 3.3 times in the direction, stretching 3.3 times in the direction perpendicular to the direction.
The sound was extended.

Next, a film (thickness 10
The following table shows the results of investigating the characteristics of 0 mountain). Incidentally, almost no decomposition or sublimation of the organic compound was observed during the test film T, and a film could be obtained smoothly. For comparison, we made a biaxially stretched film and an unstretched film that did not contain the organic compound, and an unstretched film that contained the organic compound (each 100 μm thick) with the same formulation, and measured the physical properties. It is listed in the same table. Comparative Examples 4 to 5 Examples 2 to 6 Coefficient of friction of biaxially stretched polyethylene terephthalate film (#25) produced in the same manner as in Example 1 by changing the concentration of the organic compound added (however, the heat treatment temperature was 200 oo) , and intrinsic viscosity are shown in the table below.

If the intrinsic viscosity is less than 0.5, the film properties will be poor and it will be difficult to use, so the amount of the organic compound of the present invention added must be 5% by weight or less. Example 7 Comparative Examples 6 to 9 1.5% of each organic compound was added to polyethylene terephthalate (intrinsic viscosity 0.70) polypropylene (intrinsic viscosity 1.5 in tetralin at 135°C)
4) After mixing with Amo resin, polyethylene (intrinsic viscosity 1.48 in decalin at 135°C), and nylon 6 powder, it was melt-extruded under the conditions shown in the following table to make an unstretched film, which was biaxially stretched in the longitudinal and transverse directions. .

Polyethylene terephthalate 2-layer stretched film was transparent, but polypropylene, ABS resin, polyethylene, and nylon 6 all became clearly opaque or extremely colored, making them unsuitable as products from the beginning or having a wavelength of 55 h#. The light transmittance was poor. The thickness of each film is 20 to 30 mm. * Uniform stretching is extremely difficult Example 8 2.5% of the following organic compound was mixed with polyethylene terephthalate copolymerized with 5% isophthalic acid, and the unstretched film was melt-extruded in an extruder heated to 280:00. Made, then 85qo, 3.3 per axis
220°C after stretching 3.7 times at 92°C in the direction perpendicular to this
heat treated.

The wavelength of the obtained biaxially stretched film with a thickness of 50 mm is 55 mm.
The light transmittance of the film is 83%, and the bending resistance after heat treatment (24000, 1 hour), which is an index of heat resistance, is about the same as that of a stretched film made using the same method without adding the organic compound. The sound was louder than that of 1, and the coefficient of friction was 0.71 compared to 0.78, which was 4.0, and the slipperiness was significantly improved. Comparative Example 10 The dynamic friction coefficient and intrinsic viscosity of a Nifuji stretched polyethylene terephthalate film prepared in the same manner as in Example 4 by adding 2% by weight of an organic compound having the following chemical structure are shown in the following table.

Its intrinsic viscosity was significantly lower than that of the film of Example 4. Comparative Example 11 Stearic acid, known as a lubricant for films,
2.6-di-tert-butyl-P-cresol (manufactured by Shell Chemical Co., Ltd., trade name "Ionol"), known as a heat resistant agent
were added in an amount of 2% by weight in the same manner as in Example 1 to form two stretched polyethylene terephthalate films (thickness 1
00 Buddha) was created.

The results of investigating the properties of this film are shown in the table below. Stearic acid significantly lowered the intrinsic viscosity. Furthermore, 2.6 di-tert-butyl-P-cresol had no effect on heat resistance and significantly impaired the transparency of the film. Proportions 13 to 31 Using the same method as in Examples, No. 1 shown in Table 1 of JP-A-50-74579 was used. 1~No. 20 (M.3 is an organic compound used in the present invention and is omitted because it was shown in Example 1 and Comparative Example 2) was added in an amount of 2% each to poly-IJ ethylene terephthalate to prepare an unstretched film and a biaxially stretched film. A film was made, and the heat resistance before and after heat treatment was measured, and the results are shown in the table below.

Claims (1)

[Claims] 1 (1) Contains 0.1 to 5% by weight of an organic compound represented by the chemical structural formula ▲ Numerical formula, chemical formula, table, etc. ▼ (where R represents a methyl group or ethyl group) A polyethylene terephthalate film characterized in that it is oriented in two axial directions.