JP2555707B2 - Process for producing polyethylene 2,6-naphthalate film - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polyethylene 2,6-naphthalate film, which is a biaxially stretched polyethylene 2,6-naphthalate film, and particularly has an increased strength in the machine direction. Another object of the present invention is to provide a production method having excellent film-forming stability when producing an asymmetrically oriented biaxially stretched polyethylene 2,6-naphthalate film.

(Prior Art) Generally, polyester typified by polyethylene terephthalate has excellent physical and chemical properties, so that it can be used for magnetic tapes, floppy disks, photographs, capacitors, packaging in addition to fibers and moldings. It is also widely used as a film for radiography and X-ray.

Particularly in the field of magnetic tape, a base film containing polyethylene terephthalate as a main component is used in a wide range, and its application range tends to be further expanded. on the other hand,
With the advancement of technology, downsizing of devices and magnetic tapes is required, and therefore it is necessary to make the base film even thinner, that is, to have higher strength. For example, when manufacturing a base film made of polyethylene terephthalate, it is uniaxial. Tensileizing, which strongly stretches the tape to increase the strength of the tape, is used.

(Problems to be Solved by the Invention) However, when polyethylene terephthalate is used as a raw material and tensilized, the stress at the time of 5% elongation of the obtained base film is about 20 kg / mm ^{2 at the} maximum, which is insufficient for the demand of the industry. It was Further, by adopting special stretching conditions, even if a base film satisfying the strength requirement is obtained, the strength and other properties, such as heat shrinkage properties, tend to conflict with each other. When the metal vapor deposition method is used to process the base film into a magnetic tape, the base film is heated to 100 ° C. or higher, so that heat shrinkage occurs and the quality is deteriorated.

Various base films have been proposed for the purpose of solving these problems, and polyethylene 2,6-naphthalate film is known as one of them.

However, in order to satisfy both strength and heat resistance at the same time, the conventional re-longitudinal stretching method consisting of longitudinal / transverse / longitudinal stretching or
It is also necessary for polyethylene 2,6-naphthalate film to be subjected to a longitudinal stretching method. In particular, when forming a film that is a thin film such as a base film for 8 mm video and is required to have a high strength in the longitudinal direction, the productivity is lowered by the conventional re-longitudinal stretching method and the transverse / longitudinal stretching method. However, there is a problem that the quality unevenness is large due to the instability of the process. That is, in the re-longitudinal stretching method, the film is stretched in the longitudinal direction and the transverse direction to significantly advance the orientation and crystallization, and the film whose main orientation direction is the transverse direction is re-oriented in the longitudinal direction to re-orient the molecular chains. Back in the vertical direction,
There has been a problem that a large amount of energy is required for the stretching and that the film is easily broken. Further, in the transverse / longitudinal stretching method, since a wide film once stretched in the transverse direction is stretched at a high ratio in the longitudinal direction, film tearing easily occurs during the longitudinal stretching, and the process is unstable. Therefore, there was a problem that the quality unevenness was large.

(Means for Solving the Problems) In view of the problems of the above-mentioned conventional techniques, the inventors of the present invention, in a method for producing a stretched polyethylene 2,6-naphthalate film, carry out re-longitudinal stretching after transverse / longitudinal stretching. By doing so, it is intended to provide a method for producing a polyethylene 2,6-naphthalate film having high strength and improved operational stability.

That is, the present invention is a biaxially oriented film obtained by sequentially stretching a substantially unoriented film mainly composed of polyethylene 2,6-naphthalate in the transverse direction and the longitudinal direction at a temperature of 100 to 170 ° C. by a factor of 2.5 to 5.5. And then 1.05 ~ at 100 ~ 180 ℃ in the vertical direction.
A method for producing a polyethylene 2,6-naphthalate film, which comprises re-drawing to 2.00 times and heat-setting at 160 ° C. to a temperature lower than the melting point of the film.

The above-mentioned substantially unoriented film mainly composed of polyethylene 2,6-naphthalate is a polymer, a copolymer or a mixture thereof having a molecular constitution of 80 mol% or more consisting of polyethylene 2,6-naphthalate units. As a raw material, copolymer components include terephthalic acid, P-β-
Oxyethoxybenzoic acid, 4,4'-dicarboxyl diphenyl, 4,4'-dicarboxyl benzophenol,
Bis (4-carboxylphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid,
Dicarboxylic acid components such as cyclohexane-1,4-dicarboxylic acid, propylene glycol, diethylene glycol,
Cyclohexanedimethanol, an ethylene oxide adduct of bisphenol A, a glycol component such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and an oxybenzoic acid component such as P-oxybenzoic acid can be arbitrarily selected and used. A small amount of a compound containing an amide bond, a carbonate bond or the like can be contained as other copolymerization components. The polymer may contain internal particles and external particles known as a lubricant, and stabilizers such as phosphoric acid, phosphorous acid and esters thereof. And in the present invention,
As the method for producing the polyester, it is possible to apply any production method such as a direct polymerization method in which an aromatic dicarboxylic acid and a glycol are directly reacted and a transesterification method in which a dimethyl ester of an aromatic dicarboxylic acid and a glycol are transesterified. it can.

In the present invention, a substantially unoriented unstretched film obtained by melt-extruding the polyethylene 2,6-naphthalate raw material at a temperature of 260 to 320 ° C by a usual method and cooling and solidifying is used.

In the present invention, a biaxially oriented film is obtained by transversely and longitudinally stretching the above unoriented film in the transverse direction and then in the longitudinal direction. The stretching ratio in this case is set to 2.5 to 5.5 times at a temperature of 100 to 170 ° C. in both the transverse direction and the longitudinal direction, but the transverse direction and the longitudinal direction are slightly different, and the transverse direction is 100 to 170 times. Stretched 2.5 to 4.5 times at 140 ℃, 11 in the machine direction
It is preferable to stretch at 3.0 to 5.5 times at 0 to 170 ° C.

In the present invention, the biaxially oriented film obtained by the above-mentioned transverse / longitudinal stretching is further re-stretched in the longitudinal direction, and the stretching ratio at this time is 1.05 to 2.00 times at a temperature of 100 to 180 ° C, Preferably, it is set to 1.05 to 1.70 times under the temperature of 120 to 170 ° C. The film re-stretched in the machine direction is heat-treated at a temperature of 160 ° C. to lower than the melting point of the film, preferably 200 to 250 ° C. for heat setting. The processing time is preferably 2 to 3 seconds. This heat treatment is performed by holding both ends of the re-stretched film with clips, but it may be in a relaxed state in the width direction.

(Function) In the present invention, the biaxially stretched film obtained by the transverse / longitudinal stretching method and selectively oriented in the longitudinal direction is continuously re-stretched in the longitudinal direction. In other words, the longitudinal stretching in the conventional transverse / longitudinal stretching method is performed twice. Therefore, the stretching conditions of longitudinal and transverse re-longitudinal stretching are relaxed, and even if the total stretching ratio is set to the same ratio as the conventional one, the film damage is eliminated and the operation is stable. You can measure high strength.

However, if the temperature for transverse / longitudinal stretching is less than 100 ° C, the film breaks due to a significant increase in the stress required for stretching, and if it exceeds 170 ° C, the film breaks due to crystallization that occurs during preheating. Also, during stretching, fusion of the film to the roll occurs, and the stretching ratio in the above-mentioned transverse / longitudinal stretching is 2.
If it is less than 5 times, good thickness uniformity cannot be obtained, and if it exceeds 5.5 times, film rupture occurs due to a significant increase in the stress necessary for stretching, and the conditions for transverse stretching and longitudinal stretching are set. Differently, transverse stretching 100-140 ℃, draw ratio 2.5-
4.5 times, longitudinal stretching temperature 110-170 ℃, stretching ratio 3.0
When it is performed up to 5.5 times, a film having excellent stability in film formation and excellent thickness uniformity can be obtained.

When the temperature during re-stretching is less than 100 ° C, the thickness uniformity is deteriorated due to the significant increase in the stress required for stretching.
If the temperature exceeds 180 ° C, the mechanical properties will not be improved, the uniformity of thickness will be impaired, and the stretching ratio for re-longitudinal stretching will be reduced.
If it is less than 1.05 times, the desired mechanical properties will not be improved, and if it exceeds 2.00 times, the film will rupture due to a marked increase in stretching stress, and the heat treatment temperature during heat setting will be 160 ° C. If it is less than, it cannot be provided as a product because sufficient thermal stability cannot be obtained.On the contrary, if it exceeds the melting point of the film, it leads to a decrease in the abrasion resistance of the film due to a marked increase in crystallinity, It is not preferable as a base film for magnetic tape.

After completion of the heat setting treatment, the film is heated to a temperature of 100 to 160 ° C., preferably 110 to 150 ° C. and subjected to a relaxation treatment of 0.1 to 1% in the longitudinal direction to further improve the dimensional stability. Can be made.

 The present invention will be described below with reference to examples.

The stress (F) at the time of 5% elongation of the stretched film in the examples is
-5 value) and the heat shrinkage rate were obtained by the following measuring methods.

F-5 value: A strip-shaped sample having a width of 10 mm and a length of 150 mm was cut out in parallel with the length direction and the width direction of the film, and a tensile test was performed using a Toyo Baldwin Tensilon at a deformation rate of 100% per minute. The stress when stretched by 5% was determined.

Heat shrinkage rate: A strip-shaped sample with the same shape as that used to measure the F-5 value was left in a gear oven at 105 ° C for 30 minutes without tension, and the length change of the strip-shaped sample before and after the treatment The heat shrinkage rate was calculated.

(Examples 1 to 4) After thoroughly drying polyethylene 2,6-naphthalate pellets having an intrinsic viscosity of 0.55, the pellets were fed to an extruder and melt-extruded at 290 ° C, which was then transferred to a drum cooled to 30 ° C. By contacting and cooling and solidifying, an unoriented film having a thickness of 160 μm was obtained. Next, the unoriented film was heated at a temperature of 130 ° C. in a lateral direction of 3.2.
The film was double-stretched and then stretched 4.5 times in the machine direction at a temperature of 140 ° C. to obtain a biaxially oriented film. Then, this biaxially oriented film was further stretched at a temperature of 160 ° C. in the longitudinal direction by a stretching ratio of 1.07.
Change to 4 types in the range of ~ 1.33 and re-longitudinal stretch,
The film was heat-set at 0 ° C. for 2 seconds, cooled, and wound into a film, and the high-strength film of Examples 1 to 4 (thickness 9 to 10).
μ) was obtained.

(Comparative Examples 1 and 2) An unoriented film having a thickness of 160 µ and obtained in the same manner as in Examples 1 to 4 was subjected to transverse and longitudinal stretching by a conventional method to produce a film of Comparative Example 1 (final thickness 10 µ). That is, the unoriented polyethylene 2,6-naphthalate film was heated to 130 ° C.
Stretched 3.2 times in the transverse direction with continuous stretching at 140 ℃ in the longitudinal direction at 5.2
The film was double-stretched to obtain a biaxially oriented film, which was heat set at 240 ° C. for 2 seconds, then cooled and wound. The film of Comparative Example 2 was produced in the same manner as Comparative Example 1 except that the transverse stretching ratio in Comparative Example 1 was changed to 2.8 and the longitudinal stretching temperature was changed to 145 ° C.
In both cases, the film was broken during film formation, and the final product could not be obtained.

Comparative Example 3 An unoriented film having a thickness of 160 μ and obtained in the same manner as in Examples 1 to 4 was stretched 3.2 times in the transverse direction at a temperature of 180 ° C. Subsequently, it was attempted to obtain a biaxially oriented film by longitudinally stretching at a temperature of 180 ° C by 4.5 times in the longitudinal direction and further by 1.24 times in the longitudinal direction at a temperature of 180 ° C, but the film was fused to a roll during longitudinal stretching and stretched. However, the final product could not be obtained.

Comparative Example 4 An unoriented film having a thickness of 160 μ and obtained in the same manner as in Examples 1 to 4 was stretched 5.6 times in the transverse direction at a temperature of 130 ° C., but the film was significantly broken, and the final product could not be obtained. It was

(Comparative Example 5) Polyethylene terephthalate pellets having an intrinsic viscosity of 0.60 were dried and melt-extruded at 280 ° C to obtain an unoriented film in the same manner as in Example.
Double stretching, then 4.5 times in the machine direction at a temperature of 95 ℃ to obtain a biaxially oriented film, and then re-stretch at a temperature of 130 ℃ in the machine direction at a draw ratio of 1.33 and heat setting at 210 ℃ for 2 seconds. Was applied, and the film was cooled and wound to obtain a biaxially oriented polyethylene terephthalate film (thickness 9 μm).

The manufacturing conditions and performances of Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 1 of the attached sheet. In the table, MD means the length direction of the film, and TD means the width direction of the film.

As is clear from Examples 1 to 4 in the above table, the larger the re-longitudinal stretching ratio is set, the more the F-5 value in the MD direction increases.

Comparative Example 5 is an example of a polyethylene terephthalate film, but when the total longitudinal stretching ratio is the same, both the F-5 value and the heat shrinkage ratio are inferior to the polyethylene 2,6-naphthalate film, and the film longitudinal occurrence frequency is also high. There were many.

(Effects of the Invention) The present invention is intended to carry out transverse / longitudinal stretching and then re-longitudinal stretching in the production of polyethylene 2,6-naphthalate film, and to specify the conditions. This is equivalent to performing the longitudinal stretching of the film in two steps, and by setting the total longitudinal stretching ratio to a value larger than that of the conventional one, a toughened film having a higher strength than that of the conventional one can be obtained, and moreover, breakage during film formation due to stretch molding is remarkable. Reduced, smooth operation is possible, and product quality is made uniform.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-1-188322 (JP, A) JP-A 63-60731 (JP, A) JP-A 63-17023 (JP, A) JP-A 49- 86459 (JP, A)

Claims (1)

(57) [Claims] 1. A substantially unoriented film mainly composed of polyethylene 2,6-naphthalate is arranged in the transverse direction and then in the longitudinal direction.
Sequential stretching of 2.5 to 5.5 times at a temperature of 100 to 170 ° C to form a biaxially oriented film, and then 1.05 to 2.00 at 100 to 180 ° C in the machine direction.
A method for producing a polyethylene 2,6-naphthalate film, which is re-stretched twice and heat-set at 160 ° C to less than the melting point of the film.