JPS5981138A - Manufacture of polyether ester film - Google Patents

Abstract

PURPOSE:To obtain a film with a high strength and a better running property for magnetic tapes or the like by heat treatment of a film comprising polyethylene alpha,beta-bis(2-chlorophenoxy)ethane 4,4'-dicarboxylate or the like on a specified condition after biaxial stretching thereof. CONSTITUTION:An unstretched film comprising polyether ester containing more than 85mol% of polyethylene alpha,beta-bis(2-chlorophenoxy)ethane 4,4'-dicarboxylate with the density of 1.42-1.46 is uniaxially stretched so as to range 0.06-0.23 in the double refraction within the surface of the film and 1.44-1.46 in the density and then, stretched at the right angle to this direction to make a biaxially stretched film. Then, the film thus obtained undergoes a heat treatment so as to range 1.45-1.49 in the density and 1.51-1.56 in the refractive index thicknesswise to obtain the intended film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyetherester film, and more particularly, to a method for producing a biaxially oriented polyetherester film suitable for a base film of a magnetic tape.

Conventionally, as a method for producing polyetherester film, polyethylene 1,2-diphenoxyethane 4,41
- As a method of sequentially biaxially stretching an unstretched film of dicarboxylate, for example, Japanese Patent Publication No. 11600/1982 and Japanese Patent Application Laid-open No. 97668/1989 are known.

However, such conventional methods have the following drawbacks. That is, in the former case, there are disadvantages in that sequential biaxial stretching properties are poor and thickness unevenness becomes large, while in the latter case, the stretching is carried out in an unreasonable manner, ie, ``stretching is carried out in such a way as to produce a gap sound.''

From a practical standpoint, it has the disadvantage that its stretchability is unsatisfactory. Furthermore, these conventional methods have the drawback that the mechanical strength of the obtained film is low, and when used as a base film for a magnetic tape, the running characteristics of the magnetic tape will be poor if the thickness is made thinner than a certain level. .

The purpose of the present invention is to overcome the drawbacks of the conventional methods and to (1) stabilize a polyetherester film, which has high mechanical strength and excellent running characteristics as a magnetic tape even if it is thin, using a sequential biaxial stretching method. The purpose of this paper is to provide a method for manufacturing the same.

In order to achieve all of the above objects, the present invention has a secondary structure, that is, polyethylene α,β-bis(2-bis).

An unrolled θ, θ2 Oki film made of polyether ester containing 85 or more moles of ethane 4,4'-dicarboxylate and having a density in the range of 1.42 to 1.46 is Birefringence medium tank~0,2
5. After uniaxial stretching so that the density is in the range of 1.44 to 1.46, the film is stretched in a direction perpendicular to the above direction to form a biaxially stretched film. The present invention is characterized by a method for producing a polyetherester film, which is heat-treated so that the refractive index in the thickness direction of the film is in the range of 151 to 1°56.

The polyether ester used in the present invention is polyethylene α
, β-bis(2-chlorophenoxy)ethane 4.4'-
It is necessary that the dicarboxylate unit is contained in an amount of 85 mol or more. If the single [phase] is less than 585 molar ratio,
This is undesirable because the biaxial stretchability deteriorates sequentially and the resulting film becomes unsuitable for running as a magnetic tape. Further, the polyether ester used in the present invention has an intrinsic viscosity of 0.3 to 1.4. Particularly preferred is a range of 0.4 to 1.3.

If the viscosity is lower than the above range, the stretchability tends to deteriorate, while if the viscosity is higher than this range, the mechanical strength of the obtained film will decrease.

This is not preferred because it tends to cause poor running characteristics as a magnetic tape.

The polymerization method for such a polyether ester includes 1, for example, a total transesterification reaction between a dimethyl ester of a dicarboxylic acid mainly consisting of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid and ethylene glycol. A transesterification method in which polycondensation is carried out after
α,β-bis(2-chlorophenoxy)ethane-4,4
There is a direct polymerization method in which a dicarboxylic acid mainly consisting of /-dicarboxylic acid and ethylene glycol is completely esterified and then polycondensed. What is the most convenient way?

Dimethyl ester of dicarboxylic acid mainly composed of α,β-bis(2-chlorophenoxy)ethane-4,4'-dicarboxylic acid, ethylene glycol and all esters with calcium compound and other transesterification catalyst and antimony trioxide After the exchange reaction.

This is a transesterification method in which a phosphorus compound is used as a heat-resistant agent and then polycondensed.This method produces ethylene α,β-bis(2-chloro), which contains less diethylene glycol and has good heat resistance and good film formability and stretchability. A polyether ester having phenoxy)ethane-4,4/-dicarboxylate units as the main constituent unit can be obtained.

An unstretched film is made from the above polyetherester pellets, and the density of this unstretched film is 1.42.
~1.46, preferably 1.42-1.45. If the density of the unstretched film is higher than the above range, the subsequent biaxial stretching, especially the second axis, will be poor, and the film will often break or the thickness will become uneven, which is not preferable.

Next, from this unstretched film, when uniaxially stretched, the film was ~0.2
0, density 1.44-1.46 preferably 1.445
Must be within the range of ~1.455.

- If the birefringence of the axially stretched film is smaller than the above range, the subsequent second-axis stretching will not be uniform, the film will become uneven in thickness, and the film will whiten or wrinkle during heat treatment. On the other hand, if the birefringence is larger than the above range, it is not preferable because the film often breaks during the subsequent second-axis stretching or the thickness becomes uneven. If the density is lower than the above range, it is not preferable because the subsequent second-axis stretching will not be uniform and the thickness will become uneven.On the other hand, if the density is higher than the above-mentioned range, the second-axis stretching This is not preferable because the film often breaks during axis stretching and the thickness becomes uneven.

Next, this biaxially stretched film is stretched in a direction perpendicular to the previous stretching direction to form a biaxially stretched film. In this biaxial stretching, the in-plane birefringence of the film is 0~o, i'o, and if the film is well-defined, it is O.
It is desirable that it be within the range of ~005. If the birefringence is larger than the above range, wrinkles are likely to occur during subsequent heat treatment, and the resulting film tends to have poor running characteristics as a magnetic tape, which is not preferred.

Next, this biaxially stretched film is heat treated, and the film after heat treatment has a density of 1.45 to 1.49, preferably 1.
46-1.48. The refractive index in the film thickness direction is 1.51
~1.56. It should preferably be within the range of 1.52 to 1.55. If the density of the film is lower than the above range, the resulting film will have poor dimensional stability and will not be suitable as a base film for magnetic tape.

On the other hand, if the density is greater than the above range, the running characteristics of the magnetic tape will be poor, which is not preferable. In addition, it is difficult to produce a film whose refractive index in the film thickness direction is smaller than the above range, and furthermore, the resulting film has poor running characteristics as a magnetic tape, which is undesirable. If the refractive index is larger than the above range, the thickness unevenness of the obtained film will increase,
Moreover, it is not preferable because the running characteristics as a magnetic tape become poor.

Note that the in-plane birefringence of the heat-treated film of the present invention is desirably within the range of 0 to 0, io, preferably 0 to 0.05. If the birefringence is larger than the above range, the resulting film tends to have poor running characteristics when used as a magnetic tape, which is not preferred.

Next, a specific manufacturing method for obtaining the occlusion, birefringence, and refractive index in the thickness direction of the present invention will be explained.

First, the intrinsic viscosity is 0.3 to 1.4. Preferably 0.4-1
．． A pellet of polyethylene α,β-bis(2-chlorophenoxy)ethane 4,4'-dicarboxylate having a range of 3 is sufficiently vacuum-dried and then fed to a known melt extrusion method, preferably at 275 to 310°C. nij285~
It is melt-extruded into a sheet through a slit-shaped die at 610°C, wound around a casting drum whose surface temperature is controlled at 20-80°C, and cooled and solidified to form an unstretched film. In this case, an electrostatic casting method is effective for uniformly rapidly cooling. Next, while preheating this unstretched film to 70-125°C, preferably 80-120°C, the stretching temperature is 80-160°C, preferably 90-120°C.
It is stretched 25 to 3.8 times, preferably 3 to 65 times, in the longitudinal direction at 125° C. and at a stretching speed of 10 to 10 times per minute.

Next, this uniaxially stretched film was stretched at 105°0 to 1 gs'a
, preferably at a temperature of 115-150°C and a stretching speed of 1
Stretching 28 to 4.3 times in the width direction, preferably 30 to 670 to 67 times, at a rate of 0 to 10 times per minute.9 In the biaxial stretching of the present invention, the stretching time ratio satisfies formula (A). It is preferable to do so. However, X is the stretching ratio in the longitudinal direction of the film, and y is the stretching ratio in the width direction of the film. Stretching ratio is smaller than the range of formula (A) 12≦x” 10y
”≦28 ・・・・・・・・・・・・・・・・・・
- (A) If the film is too small, not only will the thickness of the film become more uneven and wrinkles more likely to occur during heat treatment, but the running properties of the obtained film as a magnetic tape will also be poor. On the other hand, if the stretching ratio is larger than the range of formula (A), not only will the film be more likely to break during stretching, resulting in poor stretchability and increased thickness unevenness, but also This is not preferable because the transparency of the film is likely to be impaired and the breaking strength of one mechanical strength is likely to be reduced.

Next, this biaxially stretched film is relaxed in the 9 width direction to the original length (0 to 10%, preferably 0 to 5%) at a temperature of 200 to 260'C, preferably 220'C.
The method of the present invention is completed by heat treatment at ~245° C. for 1 hour for 0.5 to 120 seconds, preferably 1.0 to 60 seconds.

Although the above description has been made regarding the case where the unstretched film is stretched in the order of the longitudinal direction and the width direction, this order may be reversed and stretched in the order of the width direction and the longitudinal direction.

Although the present invention is characterized by the method described above, by subjecting the film obtained by the present invention to a known corona discharge treatment (in air, nitrogen, carbon dioxide, etc.), A film with even better adhesion to magnetic Ji and the like can be obtained. Further, for the purpose of imparting adhesion, lubricity, surface smoothness, etc., other types of polymers can be laminated or other types of compositions can be entirely coated.

In addition, if the polyether ester used in the present invention has less than 15 molar units, it may contain other copolymer components. In this case, the copolymerization components include terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid*'
Dicarboxylic acids such as 4+''-biphenyldicarboxylic acid, α,β-bis(phenoxy)etha:y4.4'-dicarboxylic acid, or.

Dioxy compounds such as propylene glycol and 1,4-cyclohexane dimetatool are common.

Another example is the polyether ester used in the present invention.

Other types of polymers may be incorporated within the range that does not impede the purpose of the present invention, and inorganic or organic agents such as antioxidants, heat stabilizers, surface protrusion forming agents, nucleating agents, and ultraviolet absorbers may be incorporated. Additives may be added in amounts that are normally added.

The characteristic values of the present invention are based on the following measurement method and criteria number.

+l) Mechanical strength (a) Measuring method According to the method specified in J Engineering 5-Z-1702,
Using an Instron type tensile tester, Young's modulus,
F5' (tensile strength at 5% bending length) and breaking strength are 2
Measured at 5°C, 165°RH.

(b) Each physical property value (Young's modulus, F
5. When both of the following physical properties (breaking strength) were satisfied, the mechanical strength was determined to be pierced, and in other cases, the mechanical strength was determined to be low.

■Young's modulus≧550 y/mm' ■F 5215 kg/mm' ■Breaking strength≧25 kg/nu2 (2) Running characteristics as a magnetic tape C0-Ni is used as a magnetic layer on a 6 μm thick film.
The alloy was formed to a thickness of 1,000× by electron beam evaporation to form a magnetic tape. The running conditions of this tape were examined in all commercially available home video tape recorders. 〇(3) Dimensional stability The sample film was cut out to a width of 10 m and a length of 250 mm.
Place two gauge lines at a distance of about 200 mm, and measure the distance accurately (this is defined as Am). After applying a full load of 3.0 g to the tip of this sample and leaving it for 50 minutes in a hot air oven at 150°C, measure the distance between the marked lines. A-B)/
A'z is the heat shrinkage rate. A film with a heat shrinkage rate of less than 4 inches in both the longitudinal and width directions was judged to have good dimensional stability, and a film with a heat shrinkage rate of 4 inches or more in one or both directions was judged to have poor dimensional stability.

(4) Uneven thickness of the film Measure the thickness continuously in the width direction of the film (the etched part was cut) (the total width of the film is 1 m). Divide the difference between the maximum and minimum thickness by the average thickness, and add 100 to this difference.
Multiply by and use the displayed value as the thickness unevenness. This value is 1
If the coefficient was less than 0, the thickness unevenness was determined to be good, and if it was 10 or more, the thickness unevenness was determined to be poor.

(5) Stretchability If the biaxial stretching film forming operation is performed continuously for 10 hours, and the film breaks 0 to 1 times during that time, the stretchability is good, and if the film breaks 2 or more times, the film is broken 2 times or more. It was determined that the stretchability was poor.

(6) Birefringent sodium D-line (wavelength 589 nm) i Place the sample film surface perpendicular to the optical axis in a polarizing microscope with crossed nicol gold polarization as the light source.

The optical path difference F caused by the birefringence of the sample is determined from the compensation values of all compensators (lines).

ro/d (absolute value>) is defined as birefringence. Here, or the thickness of the sample film.

Measurements were performed at 25°C and 165% RH.

(7) Refractive index in the thickness direction Sodium D line (wavelength 589 nm) Measured using an Atsube refractometer as an i light source.

In addition, methylene iodide was used as the mounting solution, and the measurement was carried out at 25
Performed at °C.

(8) Density Measured at 25°C using a density gradient backing made of carbon tetrachloride and n-hebutane.

(9) Intrinsic viscosity It was determined from the value of relative viscosity measured at 25°C in 0-chlorophenol.

As described above, the present invention uses a specific polyetherester as a material and uses a manufacturing method that satisfies a specific range of manufacturing conditions, so the obtained film had the following excellent properties.

(1) The film has high mechanical strength and has excellent running characteristics when used as a magnetic tape even if it is thin.

(2) The film has excellent dimensional stability and is suitable as a base film for magnetic tape.

(3) The resulting film has excellent adhesive properties (for example, adhesive properties with the magnetic layer).

Furthermore, the film could be stably produced as follows.

(1) All films can be manufactured with small thickness unevenness.

(2) The film produced according to the present invention has extremely good stretchability (successive biaxial stretchability).

It can be applied to all applications where biaxially oriented polyethylene terephthalate films have traditionally been used.

Particularly suitable applications are base films for video and audio magnetic tapes, or films for magnetic disks. In particular, among the nine films produced according to the present invention, the Young's modulus in at least one direction is 600 kg/
Films with a diameter of 40 to 80 μm are particularly suitable for magnetic disks from the viewpoint of disk handling. be.

Next, the embodiments of the present invention will be fully explained based on examples. After vacuum drying at 180℃ for 3 hours,
0.05% by weight of 1 siloid with an average particle size of 6 μm was mixed. Feed this to the extruder.

Melt extruded into a sheet at 300'a, electrostatically applied,
It was wound around a casting drum with a surface temperature of 20°C using the casting method and cooled and solidified to a thickness of approximately 55 μm.

A substantially unoriented, unstretched film with a density of 1.43 was prepared. The entire unstretched film was preheated to 80°C and stretched 30 times in the longitudinal direction at a stretching temperature of 110°C. This extension 1
11! ], is performed by the difference in circumferential speed between the two sets of rolls,
The stretching speed was 50,000%/min.

The birefringence of the biaxially stretched film thus obtained was 0.15.
．． The density was 1.452. - the rolled film;
33 in the width direction while heating to 120℃ using a stenter
I groaned twice. The stretching speed in this case is 5. It was O'00 chi/min. This biaxially stretched film was heat-treated at 250° C. for 60 seconds under constant length.

A 6 μm film was obtained. The density of this film is high,
465, the refractive index in the film thickness direction was 1.54°, and the in-plane birefringence of the film was 0.04. When this film forming operation was carried out continuously for 10 hours, the film did not break even once, and the thickness unevenness was 2 cm, indicating that stable production was possible. Further, as shown in Table 1, this film had high mechanical strength and good dimensional stability, and even though it was as thin as 6 μm, it had extremely good running characteristics as a magnetic tape.

From the above, it was found that the polyetherester film 1 has high mechanical strength and excellent running characteristics as a magnetic tape even if it is thin, and can be stably produced.

Table 1 Example 2. Comparative Examples 1 to 9 From the polymer composition of Example 1, unstretched films having a thickness of about 65 μm and a density of 1.432 were made in the same manner as in Example 1. This unstretched film was preheated to 80° C. and stretched 32 times in the longitudinal direction at a stretching temperature of 1io'a.

This stretching was carried out using a difference in peripheral speed between two sets of rolls, and the stretching speed was 50,000%/min. The birefringence of the thus obtained biaxially stretched film was 0.16. Density is 1.45
It was 5. The -axis stretched film was stretched 64 times in 9 width directions while heating to 120'C using a stenter.

The stretching speed in this case was 5,000%/min. The biaxially stretched film was heat-treated at 260'c for 60 seconds under constant length to obtain a 6 μm film. The density of this film is 1.465. The refractive index in the film thickness direction is 1.53
8. The in-plane birefringence of the film was 0.03. When this film forming operation was carried out continuously for a total of 10 hours, the film broke only once, and the thickness unevenness was 1.5 Lib, indicating that stable production was possible. The properties of this film are shown in Table 2.

It has high mechanical strength, good two-dimensional stability, and
Despite being as thin as μm, the running characteristics as a magnetic tape were extremely good. but.

In the method of the present invention, as shown in the same table, stable production is difficult due to frequent film tearing and large thickness unevenness, and even if stable production is possible, 9.
A film with high mechanical strength and good running characteristics as a magnetic tape could not be obtained.

Procedural amendment, Showa, December 1998, Director General of the Patent Office, Kazuo Wakasugi1, Indication of the case, 1984 Patent Application No. 1847442, Name of the invention: Process for manufacturing polyneedle ester film3, Amendment. J
Relationship with the patent applicant's case Voluntary action5, No increase in the number of inventions due to the amendment6, Column 7 of "Detailed description of the invention" of the specification subject to the amendment, Contents of the amendment (1) Specification page 12 4th line rl 702" to r'1702 or A S 1-
M-D-882”.

(2) Same, page 20, line 18 1. ``Method of the present invention'' shall be amended to ``Method other than the present invention.''

Claims (1)

[Scope of Claims] (11) Consisting of a polyether ester containing 85 or more moles of ethylene α,β-bis(2-chlorophenoxy)ethane 4,4'-dical suspension rate.The density is 1. 44 to 1.46, and then stretched in a direction perpendicular to the above direction to obtain a biaxially stretched film with a first density of 1.45 to 1.49.Refractive index in the film thickness direction A method for producing a polyetherester film, the method comprising heat-treating the polyetherester film so that the polyetherester film is in the range of 1.51 to 1.56.