JPH066337B2 - Biaxially oriented polyester ester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyether ester film, and more particularly to a biaxially oriented polyether ester film suitable as a base film for magnetic tape.

[Prior Art] Polyethylene 1,2-diphenoxyethane 4,4′-dicarboxylate) (also known as polyethylene-α, β-bis (phenoxy) ethane 4,4 ′) is used as a biaxially oriented polyetherester film. A film obtained by biaxially stretching dicarboxylate (for example, JP-B-46-11600, JP-A-SHO)
50-97668 gazette) is known.

However, when such a conventional film is used for a magnetic tape, for example, even if it is attempted to reduce the size of the cassette and increase the recording time by thinning it, the Young's modulus is low, and it cannot be achieved. There were drawbacks such as not being able to be said to have sufficient running performance.

[Object of the Invention]

The present invention provides a biaxially oriented polyetherester film which solves the above problems, enables downsizing of equipment and longer recording time, and has excellent running properties when used as a base film of a magnetic tape. To do.

〔Constitution〕

In order to achieve the above object, the present invention comprises the following constitution, namely, a polyether ester film containing polyethylene-α, β-bis (2-chlorophenoxy) ethane 4,4′-dicarboxylate in an amount of 85 mol% or more. , The sum of the refractive indices in the longitudinal and width directions of the film is 3.305 to 3.42.
0, the difference (longitudinal direction-width direction) is in the range of -0.20 to 0.20, and the sum of Young's modulus in the longitudinal direction and the width direction is 15
It is characterized by a biaxially oriented polyetherester film having a rate of at least 00 kg / mm ² .

The polyether ester of the present invention is polyethylene-α, β
-Bis (2-chlorophenoxy) ethane 4,4'-dicarboxylate units must be contained in an amount of 85 mol% or more. When the content of the unit is less than 85 mol%, not only the running property of the magnetic tape becomes poor, but also the ductility becomes poor and stable production cannot be performed, which is not preferable. It should be noted that, of the constituent units of the polyether ester of the present invention, other copolymer components may be contained as long as they are less than 15 mol%. In this case, the copolymerization components include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,
Dicarboxylic acids such as 4'-biphenyldicarboxylic acid, α, β-bis (phenoxy) ethane 4,4'-dicarboxylic acid, or dioxy compounds such as poropylene glycol and 1,4-cyclohexanedimethanol are used.

Further, the polyether ester of the present invention may be blended with another type of polymer within a range that does not impair the object of the present invention, and an antioxidant, a heat stabilizer, a lubricant, a nucleating agent, and surface protrusion formation. And / or inorganic agents such as UV absorbers
Alternatively, organic additives may be added to the extent that they are usually added.

The polyetherester film of the present invention has a temperature of 290
℃, shear rate 200 / sec melt viscosity is 800 ~
Desirably, it is 15,000 poise, preferably 1,000 to 8,000 poise. Within this range, the impact resistance of the film and the running property when used as a magnetic tape are further improved.

The film of the present invention is a film in which the above polyether ester is biaxially oriented, and the sum of the refractive indexes in the longitudinal direction and the width direction of the film is 3.305 to 3.420, preferably 3.3.
It is necessary to be in the range of 15 to 3.3410. If the sum of the refractive indices is smaller than the above range, the running property of the magnetic tape becomes poor, which is not preferable. On the other hand, it is difficult to stably manufacture a film in which the sum of the refractive indices in the longitudinal direction and the width direction is larger than the above range, and the running property as a magnetic tape becomes poor, and the film has poor impact resistance. Therefore, it is not preferable as a base film for magnetic tape.

In the film of the present invention, the difference in the refractive index between the longitudinal direction and the width direction (longitudinal direction-width direction) of the film is in the range of -0.2 to 0.2, preferably -0.1 to 0.1. is necessary. Even if the difference in the refractive index between the longitudinal direction and the width direction is smaller than the above range,
Even if it is large, the impact resistance of the film will be poor, so it is not preferable as a base film for magnetic tape.

The sum of Young's modulus in the longitudinal direction and width direction of the film of the present invention is 1500 kg / mm ² or more, preferably 1700 k
It must be g / mm ² or more.

If the Young's modulus is less than the above range, not only the running property of the magnetic tape becomes poor, but also recording distortion easily occurs and the magnetic conversion characteristics deteriorate, which is not preferable.

The film of the present invention has a density in the range of 1.45 to 1.49, preferably 1.46 to 1.48. Within this range, the dimensional stability of the film, impact resistance, and running performance as a magnetic tape are further improved.

Next, a method for producing the film of the present invention will be described.

First, as a method for polymerizing the polyether ester used in the present invention, for example, dimethyl ester of dicarboxylic acid mainly composed of α, β-bis (2-chlorophenoxy) ethane 4,4′-dicarboxylic acid and ethylene glycol are transesterified. The transesterification method of reacting and then polycondensing, α, β-bis (2-chlorophenoxy) ethane 4,
There is a direct polymerization method in which a dicarboxylic acid mainly composed of 4'-dicarboxylic acid is subjected to an esterification reaction with ethylene glycol and then polycondensed. The most preferred method is to use a dimethyl ester of a dicarboxylic acid mainly composed of α, β-bis (2-chlorophenoxy) ethane 4,4′-dicarboxylic acid with an antimony trioxide and a transesterification catalyst such as a calcium compound, and ethylene glycol. Is a transesterification method in which a phosphorus compound is added as a heat-resistant agent after the esterification reaction, and then polycondensation is performed. By this method, ethylene α, β-bis (2-chlorophenoxy) ethane 4 with less heat resistance and less diethylene glycol is used. ,
A polyether ester having a 4'-dicarboxylate unit as a main constituent unit can be obtained.

The polyether ester pellets were sufficiently wound under reduced pressure and then fed to a known melt extruder,
An unstretched film is prepared by melt-extruding from a slit die at 0 ° C, preferably 280 to 310 ° C, winding around a casting drum whose surface temperature is controlled at 10 to 80 ° C, and solidifying by cooling. In this case, rapidly and
The electrostatic cast method is effective for uniform cooling. By setting the density of this unstretched film in the range of 1.42 to 1.46, preferably 1.42 to 1.45, the stretchability becomes particularly good, and the impact resistance of the obtained film is also particularly good. Therefore, it is desirable.

Next, this unstretched film is biaxially stretched. This biaxial stretching may be a known simultaneous biaxial stretching method or a sequential biaxial stretching method, but the stretching ratio α in the longitudinal direction and the stretching ratio β in the width direction are expressed by the following formula (1), preferably It is necessary to satisfy (2).

10.0 ≤ α ² + β ² ≤ 40.0 (1) 12.5 ≤ α ² + β ² ≤ 30.0 (2) If the draw ratio is less than this range, the final film is It is not preferable because the running property of the tape becomes poor. On the other hand, if the draw ratio is larger than this range, the drawability of the subsequent second drawing will be poor, and the impact resistance of the finally obtained film and the running property as a magnetic tape will be poor. Therefore, it is not preferable.

Further, the stretching temperature and the stretching speed are not necessarily constant depending on the stretching method, but in the case of simultaneous biaxial stretching, the stretching temperature and the stretching speed are 80 to 130.
Stretching temperature 100-140 ° C, preferably 110-1 while preheating to a temperature in the range 90 ° C, preferably 90-125 ° C.
It is desirable to perform stretching at 30 ° C. and a stretching rate of 10 ³ to 10 ⁵ % / min, and 60 to 125 in the case of sequential biaxial stretching.
Temperature of 80 to 140 ° C., preferably 70 to 120 ° C., while preheating to a temperature of 80 to 140 in the longitudinal direction using a roll.
° C., preferably 90 to 130 ° C., stretching rate ^of 10 ³ to 10 ⁶
% / Minute to obtain a uniaxially stretched film, which is stretched by a stenter at 90 to 130 ° C., preferably 100 to
While preheating to a temperature in the range of 120 ° C, it is desirable to stretch in the width direction at a stretching temperature of 100 to 140 ° C, preferably 110 to 130 ° C, and a stretching speed of 10 ³ to 10 ⁵ % / min. The above-mentioned sequential biaxial stretching has been described in the case of stretching in the longitudinal direction and the width direction in order, but the stretching may be performed in the reverse order.

This biaxially stretched film has a sum of refractive indexes in the longitudinal direction and the width direction of 3.295 to 3.410, preferably 3.300 to 3.33.
It must be in the 0 range. If the sum of the refractive indices is smaller than the above range, the running property of the finally obtained film as a magnetic tape becomes poor. On the contrary, if the sum of the refractive indices is larger than the above range, the following 2 Not only is the stretchability of the second stretch poor, but the impact resistance of the resulting film is poor, which is not desirable.

The density of this biaxially stretched film is 1.42 to 1.47,
Preferably, it is in the range of 1.43 to 1.46, followed by 2
It is desirable because the stretchability of the second stretch, the impact resistance of the finally obtained film, and the running property when the film is used as a magnetic tape are particularly good.

Next, the thus obtained biaxially stretched film is further stretched by a roll or a stenter (this is called the second stretching). Stretching may be performed in the longitudinal direction only, in the width direction only, or in both the longitudinal direction and the width direction sequentially or simultaneously. However, the stretching ratio γ in the longitudinal direction and the stretching ratio δ in the width direction are expressed by the following formula (3 ), Preferably the following expression (4) must be satisfied.

2.2 ≦ γ ² + δ ² ≦ 15.0 (3) 2.5 ≦ γ ² + δ ² ≦ 8.5 (4) Where, for example, when stretching only in the longitudinal direction, δ = 1
Becomes

If the draw ratio is smaller than the above range, the running property of the obtained film when used as a magnetic tape becomes poor, which is not preferable. On the other hand, if the stretching ratio is larger than the above range, not only the drawability becomes poor, but also the impact resistance of the obtained film becomes poor, which is not preferable as a base film for a magnetic tape.

Although the stretching temperature and the stretching speed of the second stretching are not necessarily constant depending on the stretching method, the stretching temperature 1 and the stretching temperature 1 are preheated to a temperature in the range of 80 to 150 ° C, preferably 90 to 140 ° C.
It is desirable to carry out at a temperature of 00 to 190 ° C., preferably 110 to 180 ° C., and a stretching speed of 10 ³ to 10 ⁶ % / min.

Further, this film may be heat-treated if necessary.
The heat treatment in this case can be carried out by a known method such as in an oven or on a roll, but at a temperature of 200 to 260.
℃, preferably 210 ~ 250 ℃, time 0.1 ~
It is generally performed for 120 seconds, preferably for 1 to 60 seconds, and the film density after heat treatment is 1.45 to 1.4.
The range of 9, preferably 1.46 to 1.48 is desirable because the resulting film has particularly good impact resistance and dimensional stability. Further, during such heat treatment, the heat treatment may be performed while relaxing in the longitudinal direction and / or the width direction.

Further, the film of the present invention may be subjected to a known corona discharge treatment (in air, in nitrogen, in carbon dioxide gas, etc.), and may be used, or the adhesiveness, moisture resistance, heat sealability, lubricity, surface smoothness, etc. For the purpose of imparting the above, it may be used in the form of being laminated with another type of polymer or in the form of being coated with another organic and / or inorganic composition.

The characteristic values of the present invention are based on the following measuring methods and evaluation criteria.

(1) Young's modulus Measured at 25 ° C. and 65% RH using an Instron type tensile tester according to the method specified in JIS-Z-1702 or ASTM-D-882.

(2) Running property as magnetic tape A CO-NI alloy was formed as a magnetic layer on a sample film having a thickness of 5 μm by an electron beam evaporation method so as to have a thickness of 1000 Å, to obtain a magnetic tape. This tape is checked with a commercial home video tape recorder (helical scan) while repeatedly starting and stopping to check the running state. If it runs smoothly without causing edge folds (seaweed, etc.) or tape tearing, the running is good. If breakage or tearing of the tape occurred, it was determined that the running property was poor.

(3) Impact resistance The Charpy impact strength (unit: kg · cm / mm ² ) of the film was measured using a Jalpy impact tester manufactured by Toyo Seizo Seisakusho according to the method specified in ASTM-D-256. The values used were the arithmetic mean values when the lengthwise direction of the film was set horizontally between two fulcrums and when the widthwise direction of the film was set horizontally. When the Charpy impact strength was 20 or more, the impact resistance was good, and when it was less than 20, the impact resistance was poor.

(4) Dimensional stability (heat shrinkage rate) A sample film is cut into a width of 10 mm and a length of 250 mm, two marked lines are inserted at intervals of about 200 mm, and the intervals are accurately measured (this is Amm). . 3.0 at the tip of this sample
3g in a hot air oven at 150 ° C with a load of 3g
After leaving for 0 minutes, the marked line interval was measured (this is Bmm), and 100 × (A−B) / A was taken as the heat shrinkage rate. Dimensional stability is good when the arithmetic average value of the heat shrinkage values in the longitudinal and width directions of the film is less than 5.0%, 5.0
When it was at least%, it was determined that the dimensional stability was poor.

(5) Stability of production (stretchability) A series of operations (winding speed: 13.5 m / min) in which an unstretched film is biaxially stretched and then further stretched are continuously performed for 10 hours, during which time Torn film is 0
When it was within the range of once, it was determined that the stretching was good, and when it was broken twice or more, it was determined that the stretchability was poor.

(6) Refractive index of film The sodium D ray (wavelength 589 nm) was used as a light source and measured using an Atsube refractometer. In addition, a sulfur-methylene iodide solution was used as the mount solution, and the measurement was performed at 25 ° C. and 65% RH.

(7) Film Density (g / cm ³ ) It was measured at 25 ° C. using a density gradient tube composed of carbon tetrachloride and n-heptane.

(8) Melt viscosity Using a Koka flow tester, the viscosity was measured at a temperature of 290 ° C and a shear rate of 200 / sec.

[Action]

The present invention uses a specific polyether ester as a material,
Since it is a biaxially oriented polyetherester film having a specific range of refractive index and Young's modulus, many extended chain crystals (crystals in which molecules are stretched) are generated, and the following excellent effects are obtained. I was able to do it.

〔The invention's effect〕

The film of the present invention (1) can be miniaturized by thinning the device and lengthening the recording time, and even if it is thin, it has excellent running properties when used as a magnetic tape.

(2) Even though it is thin, it has excellent electromagnetic conversion characteristics when used as a magnetic tape.

[Use]

The film of the present invention can be applied to all the applications where a biaxially oriented polyethylene terephthalate film has been conventionally used, but a particularly suitable application is a base film for magnetic tapes for video and audio. The thickness of the film of the present invention is not particularly limited, but for a magnetic tape, a film of 4 to 12 μm, preferably 4 to 8 μm is suitable for downsizing the magnetic tape and extending the time.

Example 1 Pellets of polyethylene-α, β-bis (2-chlorophenoxy) ethane 4,4′-dicarboxylate having a melt viscosity of 2,000 poise were dried under reduced pressure at 180 ° C. for 3 hours, and then the extruder (screw) was used. Diameter: 35 mm), 30
It is melt-extruded into a sheet at 0 ° C, wrapped around a casting drum with a surface temperature of 20 ° C by the electrostatic cast method and cooled and solidified. It has a thickness of about 110 μm and a density of 1.43, and is substantially non-oriented. An unstretched film was made. This unstretched film was stretched 3.0 times in the longitudinal direction at a stretching temperature of 120 ° C while preheating to 110 ° C. This stretching was performed by the difference in peripheral speed between the two rolls, and the stretching speed was 50,000% / min. The uniaxially stretched film thus obtained was stretched 3.3 times in the width direction at a stretching temperature of 120 ° C. while preheating to 110 ° C. using a stenter. Furthermore, while preheating this biaxially stretched film to 140 ° C., at a stretching temperature of 150 ° C. in the longitudinal direction,
The film was stretched 1.5 times at the same time in the width direction and further heat-treated at 230 ° C. for 15 seconds in an oven under constant length to obtain a film having a thickness of 5 μm. The sum of the refractive indices in the longitudinal and width directions of this film is 3.33, and the difference (longitudinal direction-width direction) is -0.005.
And the sum of Young's moduli in the longitudinal and width directions is 2,000.
It was kg / mm ² . The value of this Young's modulus is about twice that of the film before the second stretching, and it can be seen that the effect of the second stretching is extremely large. Despite being as thin as 5 μm, this film had very good running properties as a magnetic tape, and had good dimensional stability and impact resistance.

Example 2 Comparative Examples 1 to 6 Biaxially stretched film having a thickness of about 9 μm produced in the same manner as in Example 1 (the sum of Young's modulus in the longitudinal direction and the width direction: 1.100 kg).
/ Mm ² ) while preheating to 130 ℃, stretching temperature 140 ℃
Was stretched 1.7 times only in the longitudinal direction. This drawing is performed by the difference in peripheral speed between the two sets of rolls, and the drawing speed is 50,000.
% / Min. Further, this film was heat-treated in an oven at a constant length at 230 ° C. for 5 seconds to obtain a film having a thickness of 5 μm. The sum of the refractive indices in the longitudinal direction and the width direction of this film was 3.32, the difference was 0.04, and the sum of the Young's modulus in the longitudinal direction and the width direction was 2,400 kg / mm ² .

The ratio of this Young's modulus value to the Young's modulus of the above-mentioned film stretched for the second time (simple biaxially stretched film) is 2.
2 (see Table 1), and it can be seen that the effect of the second stretching is extremely large. As shown in Table 1, this film had a very good running property as a magnetic tape, despite its thinness of 5 μm. In addition, this film has good dimensional stability and impact resistance,
When the operation of producing the film was continuously performed for 10 hours, the film broke only once, and the stretchability was good.

However, outside the present invention, as shown in Table 1, even if
Even if the film was stretched a second time, it was not possible to obtain a magnetic tape with excellent running properties even if it was thin. Further, from the table, it is understood that the film of the present invention has a significantly higher Young's modulus by the second stretching than the other films of the present invention. That is, only a film having a specific range of refractive index and Young's modulus obtained by biaxially stretching a specific polyether ester under specific conditions and then re-stretching, is excellent as a magnetic tape even if it is thin. It turns out that it shows sex.

Claims (1)

[Claims] 1. Polyethylene-α, β-bis (2-chlorophenoxy) ethane 4,4'-dicarboxylate
Consisting of a polyether ester film containing more than mol%, the sum of the refractive indices in the longitudinal and width directions of the film is 3.30.
5 to 3.420, difference (longitudinal direction-width direction) is -0.20 to 0.
A biaxially oriented polyetherester film having a range of 20 and a sum of Young's modulus in the longitudinal direction and the width direction of 1500 kg / mm ² or more.