JPS58118220A - Preparation of biaxial orientated polyethylen terephthalate film - Google Patents

Abstract

PURPOSE:To obtain a film of which mechanical strength in longitudinal direction is high by such an arrangement wherein a substantially non-orientation polyethylene terephthalate film is multistage extended under certain conditions, and next, the film is extended laterally, and then it is further extended longitudinally again, and at this time, the product of an extension multiple of each extension shall be made larger than 25 times. CONSTITUTION:A film made of substantially non-oriented polyethylene terephthalate is multi-stage extended so that its non-crystal orientation coefficient becomes 0.6-1.0, and its double refraction rate becomes 0.02-0.1, and next it is extended laterally at an extension multiple of 2.5-4.5 times, and further it is extended longitudinally again at an extension multiple of 1.5-2.5 times and further the product of those multiples of multi-stage extension, lateral extension and longitudinal extension shall be made larger than 25 times. By this arrangement, it is possible to stably manufacture polyethylene terephthalate film of which mechanical strength in the longitudinal direction is high.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method for stably manufacturing a polyethylene terephthalate film having high mechanical strength in the machine direction (longitudinal direction).

Conventionally, as a method for manufacturing a film having high mechanical strength in the longitudinal direction, a method is known in which a biaxially stretched film that has been stretched in both longitudinal and transverse directions is longitudinally stretched again.

However, in such conventional methods, the mechanical strength of the produced film, that is, the F-5 value, is about 20 [10 kg
/a'' and those having an F-5 value higher than that were difficult to produce stably.

The object of the present invention is to eliminate the drawbacks of the prior art and to
It is an object of the present invention to provide a method that can stably produce one or more films having a 5 value of 2500 kg/.

CF-5 (direct wire 3 extension time input) The present invention has the following configuration to achieve the above object.

That is, a film made of substantially unoriented polyethylene terephthalate has an amorphous orientation coefficient of 0.6 to
1.0. Multi-stage stretching so that the birefringence index is 0.02 to 0.1, followed by lateral stretching at a stretching ratio of 2.5 to 4.5 times,
Further longitudinal stretching is performed again at a stretching ratio of 1.5 to 2.5 times, and
The product of each stretching ratio of the multi-stage stretching, horizontal stretching, and longitudinal re-stretching is 25
The present invention is characterized by a method for producing a biaxially oriented polyethylene terephthalate film having a biaxially oriented polyethylene terephthalate film of at least twice the size of the film.

The polyethylene terephthalate applied to the present invention is
A polyethylene terephthalate containing polyethylene terephthalate and a third component of 20 or less. Furthermore, polyethylene terephthalate is synthesized by combining terephthalic acid or its functional derivative with ethylene glycol or its functional derivative in the presence of a catalyst under appropriate reaction conditions, but before the polymerization of the polyethylene terephthalate is completed, Alternatively, one or more appropriate fifth components may be added later to form a copolymerized or mixed polyester. Suitable third components for copolymerization include compounds having ester-forming functional groups. In addition, stabilizers such as phosphoric acid, phosphorous acid and their esters, titanium oxide, fine particle silica,
It may also contain a lubricant such as calcium carbonate. In addition.

The preferred intrinsic viscosity of polyethylene terephthalate is 04
-1.0, more preferably 0855-0.8.

A film that is not substantially oriented is a film (or sheet) made of the above-mentioned melted polyethylene tere-7 tallate.
It is extruded onto a cooling drum as a shape, cooled and solidified, and is not stretched to impart orientation.

In order to carry out multi-stage stretching to obtain substantially unoriented polyethylene terephthalate, in the multi-stage stretching that utilizes the difference in circumferential speed of the rolls, the first stage is as follows.

The stretching temperature is 110-150°C, preferably 115-1
65°C9 stretching ratio 1.3 to 3.0 times, preferably 1
, 5 to 2.5 times, and the temperature and stretching ratio are lower than the temperature of the subsequent second or second stage, and the stretching ratio is within the range of 2.0 to 40 times, preferably 2.0 to 3.0 times. .

The temperature of the first stage and/or the temperature of the second stage,
When the temperature is lowered below this range, the birefringence index exceeds 0.1. Further, when the temperature of the first stage and/or the temperature of the second stage is increased above the above temperature range, the amorphous orientation coefficient becomes 0.6 or less.

If the amorphous orientation coefficient and birefringence index are outside the ranges mentioned above, the film may not be obtained due to breakage during the subsequent transverse and longitudinal stretching, or even if a film is obtained, it may be defective in physical properties or quality. It may be sufficient or it may be uneven.

Although the crystallization of the unidirectionally stretched film does not proceed, it is presumed that only the amorphous portion can be highly oriented by combining the stretching with the unidirectionally stretched film, which contributes to high strength and stable manufacturing. it is conceivable that.

Note that the amorphous orientation coefficient and birefringence are determined by the following measurement method.

(1) The amorphous orientation coefficient polyester film was coated with a fluorescent agent (Mikephor F
! The sample was immersed in a water bath containing 'rN) at 55°C and air-dried, and the polarized fluorescence intensity in the film plane was determined using a JASCO ■ FOM-1 polarimeter, and the amorphous orientation coefficient was determined according to the definition below. (F) was obtained.

F: Amorphous orientation coefficient A: Vertical polarized fluorescence intensity B: Lateral polarized fluorescence intensity (2) Birefringence Using a Pellec compensator on a polarizing microscope, the sample was collected at a temperature of 25°C and relative humidity. It was measured at 65 inches.

For transverse stretching, a so-called tenter is used, which stretches the film by sandwiching both ends of the film between replacement tubes, and the stretching ratio is set to 2.5.
~4.5 times, stretching temperature 5℃ from the second transition point of the film
Stretch at a high temperature to 13(]'0).

Re-longitudinal stretching is performed using the difference in circumferential speed between rolls in the same way as multi-stage longitudinal stretching, but the stretching ratio is 1.5.The number of stretching stages for re-longitudinal stretching may be one, but multi-stage It is more preferable that Further, it is preferable that the total longitudinal stretching ratio (the product of both the multi-stage longitudinal stretching ratio and the front longitudinal stretching ratio) is 6.0 to 12.0 times.

I cut it. Product of each stretching ratio of multi-stage stretching, horizontal stretching, and longitudinal re-stretching (
The total area stretching ratio) must be 25 times or more, preferably 28 times or more. Below this magnification, a film with high strength cannot be obtained.

In addition, the film stretched under the above conditions is then heat-set at a treatment temperature within the range of 150 to 240°C.
The thermal shrinkage rate in the longitudinal direction at 0Ω゛C is 25 coefficients or less, and the rigidity in the longitudinal direction can be further increased.

The manufacturing method of the present invention, which employs the above-mentioned method, has the following excellent effects.

11) Films with a longitudinal F-5 value of 2500 kg/■3 or more can be stably produced.

+21 By applying heat setting, a film with high strength and good dimensional stability can be obtained.

The film obtained by the present invention is suitable for applications requiring extremely thin films such as bases for magnetic recording materials, dielectrics for capacitors, and printing materials, but is particularly suitable for applications requiring extremely thin films such as bases for magnetic recording materials, dielectric materials for capacitors, and printing materials. Suitable for base film.

The present invention will be explained in more detail with reference to Examples below.
The present invention is not limited only to these examples.

Examples 1-3 Polyethylene terephthalate with IVo of 65 at 290°C
After melt extrusion, it was rapidly cooled to produce a substantially amorphous piece. Using the difference in circumferential speed of the multi-stage nip rolls, this was processed as the first stage in the longitudinal direction at 130°C.・After stretching 7 times, it was continuously stretched in the longitudinal direction for 2.
It was stretched 3 times.

The amorphous orientation coefficient of the obtained longitudinally stretched film was 0.72.

Birefringence Δn is 0.028. The density was 1.3435. Next, it was stretched 55 times in the transverse direction at 110° C. in a tenter. Do this with two more pairs of nip rolls.

A predetermined stretching process corresponding to the magnification shown in Examples 1 to 3 in Table 1-1 was carried out at 150°C and 3000 inches/min.
Tension heat fixation was performed at 00°C. The final thickness of the film is 7
~9 microns (varies depending on total area stretching ratio)
.

As shown in Table 1-2, along with the longitudinal re-stretching ratio, F
-5 value has improved to 2500/l! A high strength film with a strength of 1' or more can be obtained. Further, the thermal shrinkage rate when heated at 100° C. for 30 minutes was 2.5 inches or less. The re-longitudinal stretching ratio is 2.
Although it can be manufactured stably with almost no tearing even at 3 times the size, 2
, ruptures occur frequently at 7 times or more. The total area magnification of Examples 1 to 3 all reached 25 times or more, and in Example 6 it was 61.5.
It has doubled.

Examples 4-6 Stretching was performed in the same manner as in Examples 1 to 6. however.

In the first longitudinal stretching, the first stage was 18 times stretching at 130°C, and the second stage was 2.5 times stretching at 116°C. The obtained longitudinally stretched film had an amorphous orientation coefficient of 081 and a birefringence Δ
n is 0.041. The density was 1.3446. The longitudinal re-stretching ratio was as shown in Table 1-1. When the longitudinal re-stretching magnification was 2.5 times or more, tearing occurred frequently, but as shown in Examples 4 to B, the total area magnification was all 25 times or more, and in Example 6 it was 36.2 times.

As shown in Table 1-2, along with the longitudinal re-stretching ratio, F
-5 value has improved, both vertical F-5 values are 2500
A high strength film with a strength of 2 kg/cm2 or more can be stably obtained.

Further, the thermal shrinkage rate when heated at 100° C. for 60 minutes was 2.5 inches or less.

Comparative Examples 1 and 2.7 In both cases, the first longitudinal stretching was carried out in one step using the longitudinal (-membrane)-lateral longitudinal stretching method. Comparative Example 1 shows the longitudinal stretching conditions carried out in longitudinal-lateral stretching, that is, the case of high-magnification stretching at a low temperature, but since the obtained longitudinally stretched film has a birefringence Δn exceeding 0.1. , poor stretchability during longitudinal re-stretching.

High strength film cannot be obtained. In Comparative Example 2, an attempt was made to suppress the initial longitudinal stretching ratio and increase the re-longitudinal stretching ratio, but the amorphous orientation coefficient was low and a high strength film could not be obtained. Comparative Example 7 is an example in which the initial stretching was performed at a high temperature and a high stretching ratio, but both the amorphous orientation coefficient and the birefringence were low, and a high strength film could not be obtained. In all cases, film tearing occurred at a total vertical magnification of 6x or less, and the total area magnification did not reach 25x.

Comparative Examples 3 to 6 These are examples in which the characteristics of the longitudinally stretched film do not satisfy the conditions of the present invention in the longitudinal (two-stage) - transverse one-front longitudinal stretching method.

Comparative Example 5 shows an example in which the first longitudinal stretching was carried out in two stages at a low temperature, but the birefringence increased too much and the stretchability upon re-longitudinal stretching was poor, making it impossible to obtain a highly strong film. In Comparative Example 4, the initial longitudinal stretching was carried out at a high temperature in both stages, so both the amorphous orientation coefficient and the birefringence were low, and a highly strong film could not be obtained. In Comparative Example 5, the first stage longitudinal stretching was performed at a low temperature and the first stage was performed at a high temperature.

The amorphous orientation coefficient does not increase, and a highly strengthened film cannot be obtained. In Comparative Example 6, since the initial longitudinal stretching ratio is low, the birefringence is low and a high strength film cannot be obtained. Note that all of Comparative Examples 1 to 7 have large thermal shrinkage rates, which is not preferable.

Example 7 Two-stage longitudinal stretching and transverse stretching were carried out under the same stretching conditions as in Example 6. Next, with multi-stage longitudinal re-stretching rolls, the first stage longitudinal re-stretching was performed at 150'c to 1.5 times.

The second stage of longitudinal re-stretching was carried out at 155°C by 1.6 times.

The total longitudinal magnification was 108 times, and the total area magnification was 37.8 times. The F-5 value in the longitudinal direction is 5960 kg/. It's a winnow.

The heat shrinkage rate in the machine direction was 2.24%, and a high strength film was obtained.

Procedural amendments ``167, 'A, 29'' Director of the Patent Office Kazuo Wakasugi 1, Indication of the case Patent Application No. 670 of 1982 2, Name of the invention Method for manufacturing biaxially oriented polyethylene terephthalate film 3 , Relationship to the case of the person making the amendment Patent applicant address 2-2 Nihonbashi Muromachi, Chuo-ku, Tokyo Name
(515) Toshi Stock Company 4, Date of amendment order Voluntary 5, Number of inventions increased by amendment None 1) Specification, page 6, second line from the bottom, “150°C” is amended to “170°C” .

(2) Correct the row [0.51J of ``Comparative Example 1'' in the ``Amorphous Orientation Coefficient'' column of Table 1-1 on page 13 to ``0.96J''.

(3) The line "0.54J" in "Comparative Example 3" in the "Amorphous Orientation Coefficient" column of Table 1-1 on page 13 is corrected to [0.87J.

Claims (1)

[Claims] fil A film made of substantially unoriented polyethylene terephthalate has an amorphous orientation coefficient of 06 to 1.
．． 0. Multi-stage stretching so that the birefringence index is 0.02 to 0.1, then transverse stretching at a stretching ratio of 2.5 to 4.5 times, and further longitudinal stretching at a stretching ratio of 1.5 to 2.5 times. A method for producing a biaxially oriented polyethylene terephthalate film, characterized in that the product of each stretching ratio of the multi-stage stretching, transverse stretching, and longitudinal re-stretching is 25 times or more.