JPH03224722A - Manufacture of composite film - Google Patents

Abstract

PURPOSE:To reduce breakage to be generated at the time of manufacturing a film, and carry out smooth operation by re-orienting vertically laminated fils manufactured by the coextrusion method in which polyethylene terephthalate and polyethylene 2,6-naphthalate following the first orientation in the horizontal and vertical directions, and specifying the conditions thereof. CONSTITUTION:A composite film is formed by successively orienting non- oriented films laminated by the coextrusion method and composed mainly of films of polyethylene terephthalate as the main component and films of polyethylene 2,6-naphthalate as the main component in the order of horizontal direction and vertical direction at the temperature of 100-170 deg.C up to 2.5-5.5 times to manufacture a biaxially oriented film, and re-orienting said film in the vertical direction at the temperature of 100-180 deg.C up to 1.05-2.00 times, and then heat fixing the same at 160-250 deg.C. Thus, respective orienting conditions are relaxed by carrying out the vertical orientation in the horizontal and vertical orientation method by two times as above-mentioned, which eliminates the breakage of films and the like and stabilizes the operation, and a film of high strength and high resistance to heat can be manufactured.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a composite film.

Furthermore, in particular, heat resistance is particularly required for applications such as magnetic recording tape applications, which have high strength in the longitudinal direction by laminating a film mainly composed of polyethylene terephthalate and an oriented film consisting essentially of polyethylene 2゜6-naphthalate. The present invention relates to a method for inexpensively manufacturing a composite film suitable for vacuum-based thin film formation.

(Prior Art) Generally, biaxially oriented polyester films represented by polyethylene terephthalate are used in a wide range of applications such as magnetic tapes, electricity, and packaging because of their excellent mechanical and electrical properties.

Particularly in the field of magnetic tapes, base films made of polyethylene terephthalate are widely used, and their range of application tends to expand further. On the other hand, as technology becomes more sophisticated, there is a need for smaller devices and magnetic tapes, which requires thinner base films, that is, higher strength. Tensilizing is used to increase the strength of the tape by strongly stretching it in the axial direction. In addition, there is a demand for improved heat resistance in various applications.For example, polyethylene terephthalate is ranked in class 8 for electrical insulation applications, but materials with higher continuous usable temperatures are required. . or,
Transparent conductive films are affected by heat during vapor deposition, causing them to curl and oligomers to precipitate.
There is a demand for a film that has excellent heat resistance and a low amount of oligomer precipitation. Also, in magnetic tape applications,
When a metal vapor deposition method is used to process magnetic tapes, the base film is heated to 100° C. or higher and undergoes thermal shrinkage, so a film with heat resistance is desired. Various heat-resistant films have been proposed to meet the above requirements, and polyethylene 2,6-naphthalate film is considered promising as it has high strength, high elastic modulus, and heat resistance.

(Problems to be Solved by the Invention) Polyethylene 2,6-naphthalate film has better properties than oriented polyethylene terephthalate film in terms of various physical properties such as heat resistance, low polymerization properties, and mechanical properties.
It's extremely good.

However, in order to satisfy strength and heat resistance at the same time, it is necessary to use the conventional re-longitudinal stretching method, which involves stretching in the longitudinal and transverse directions and then further stretching in the longitudinal direction, or the transverse/longitudinal stretching method, which stretches in the order of transverse and longitudinal directions. It is necessary to use Generally, lateral stretching and longitudinal stretching are stretching perpendicular to and in the same direction as the extrusion direction, and the same applies to the present invention. In particular, when producing films that are thin and require high strength in the longitudinal direction, such as base films for 8mm videos, these conventional longitudinal re-stretching methods and transverse/longitudinal stretching methods are difficult to improve productivity. There is a problem that the deterioration is significant and there are large quality irregularities due to instability of the process. Furthermore, polyethylene 2,6-naphthalate raw material has a problem in that it is much more expensive than polyethylene terephthalate in terms of cost.

The present invention aims to produce a biaxially oriented polyethylene 2.6-naphthalate film with increased strength in the machine direction at a lower cost than a single polyethylene 2.6-naphthalate film, and to improve operational stability during production. That is.

(Means for Solving the Problems) In order to solve the above problems, the method for producing a film of the present invention combines a film containing polyethylene terephthalate as a main component and a film containing polyethylene 2,6-naphthalate as a main component. Substantially unoriented films laminated by extrusion are heated at 100 to 170°C in the horizontal and vertical directions.
A biaxially oriented film is obtained by sequentially stretching 2.5 to 5.5 times at a temperature of
This is a method for producing a composite film, which is characterized by re-stretching the film by a factor of ~2.00 and heat-setting it at 160-250°C.

The film mainly composed of polyethylene terephthalate has 40 mol% or more of its molecular composition made from polyethylene terephthalate, and the copolymerization components include naphthalene dicarboxylic acid, P-β-oxyethoxybenzoic acid, 4.4゛Dicarboxyldiphenyl, 4.4'
-Dicarboxylbenzophenone, bis(4-carboxylphenyl)ethane, adipic acid, sebacic acid, 5
-Sodium sulfoisophthalic acid, cyclohexane-1
, dicarboxylic acid components such as 4-dicarboxylic acid components, propylene glycol, diethylene glycol, cyclohexane dimetatool, ethylene oxide adduct of biphenol A, glycol components such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, P-oxybenzoic acid Oxybenzoic acid components such as the following can be arbitrarily selected and used. A small amount of a compound containing an amide bond, a carbonate bond, etc. may be included as other copolymer components. In addition, polyethylene 2
．． Films mainly composed of 6-naphthalate are made from polymers, copolymers, or mixtures thereof, in which 80 mol% or more of the molecular structure consists of polyethylene 2.6-naphthalate units. Ingredients include terephthalic acid, P-β-oxyethoxybenzoic acid, 4.4″
- dicarboxylic acid components such as dicarboxyldiphenyl, 4.4°-dicarboxylbenzophenone bis(4carboxylphenyl)ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, cyclohexane-1,4-dicarboxylic acid, Glycol components such as propylene glycol, diethylene glycol, cyclohexane dimetatool, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, P-oxybenzoic acid component, etc. can be arbitrarily selected and used. A small amount of a compound containing an amide bond, a carbonate bond, etc. may be included as other copolymer components. These, 2
Some types of polymers can contain known internal and external particles as lubricants, as well as stabilizers such as phosphoric acid, phosphorous acid and their esters.

In the present invention, the above-mentioned polyester can be produced by any production method, such as a direct polymerization method in which aromatic dicarboxylic acid and glycol are directly reacted, or a transesterification method in which dimethyl ester of aromatic dicarboxylic acid and glycol are transesterified. Can be applied.

The method for producing a composite film of the present invention is a method for producing a multilayer film consisting of a film consisting essentially of polyethylene-2,6-naphthalate and a film consisting of polyethylene terephthalate, but it may be two, three, or more layers. Moreover, the structure of the multilayer film can be arbitrarily selected depending on the purpose. Here, as a method for laminating two, three or more layers, there is also a method of bonding separately prepared films together using an adhesive, but in these methods,
It is difficult to maintain the flatness of the film, and in the present invention,
Since this is a coextrusion method in which layers are laminated in a die, there is no problem mentioned above. The melt extrusion temperature is 250~250°C for both polyethylene 2.6-naphthalate and polyethylene terephthalate raw materials.
The temperature is preferably 320° C., and the coextruded film is solidified by cooling and is used in the present invention as a substantially unoriented, unstretched film.

In the present invention, a biaxially oriented film is obtained by stretching the above-mentioned unoriented film in the transverse direction and then stretching it in the longitudinal direction. In this case, the stretching ratio is 2.5 to 5 at a temperature of 100 to 170°C in both the transverse and longitudinal directions.
．． The magnification is set to 5 times, but the magnification is slightly different in the horizontal and vertical directions, and the horizontal direction is set at 2.5 to 4 at 100 to 160 degrees Celsius.
．． Stretched 5 times, lengthwise at 110-170°C 3.
It is preferable to stretch 0 to 5.5 times.

In the present invention, the biaxially oriented film obtained by the above-mentioned transverse and longitudinal stretching is further stretched again in the longitudinal direction, and the stretching ratio at this time is 1.05 to 2 at a temperature of 100 to 180°C.
．． 00 times, preferably at a temperature of 120-170°C.
05 to 1.70 times. This longitudinally re-stretched film is then heated at a temperature of 160~160°C for heat setting.
Heat treatment is carried out at 250°C, preferably 200-250°C. The processing time is preferably 2 to 3 seconds. This heat treatment is carried out 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, a coextruded unstretched original fabric is made into a two-wheel stretched film selectively oriented by a transverse/longitudinal stretching method, and then re-stretched in the longitudinal direction. In other words, longitudinal stretching in the conventional transverse/longitudinal stretching method is performed in two steps. Therefore, the stretching conditions for horizontal and vertical stretching, longitudinal stretching, and longitudinal re-stretching are relaxed, and even if the total stretching ratio is set to the same ratio as before, film damage etc. are eliminated and operation is stable, and the A film with increased strength and high heat resistance can be obtained.

However, if the transverse/longitudinal stretching temperature is less than 100°C, the film will break due to a significant increase in the stress required for stretching, whereas if it exceeds 170°C, the film will break due to crystallization that occurs during preheating. In addition, if the stretching ratio of the tank/longitudinal stretching is less than 2.5 times, good thickness uniformity cannot be obtained; on the other hand, if it exceeds 5.5 times, the stress necessary for stretching Film breakage occurred due to a significant increase in
When the stretching ratio is 2.5 to 4.5 times at 0 to 160°C and the longitudinal stretching is carried out at a temperature of 110 to 170°C and a stretching ratio of 3.0 to 5.5 times, the film has excellent stability during film formation. A film with excellent thickness uniformity can be obtained.

Furthermore, if the temperature during re-stretching is less than 100"C, the stress required for stretching will significantly increase, resulting in deterioration of the thickness uniformity.
On the other hand, if the temperature exceeds 180°C, the film may be fused to the roll during stretching, the mechanical properties cannot be improved, the uniformity of the thickness may be impaired, and the stretching ratio for longitudinal re-stretching may be reduced. If it is less than 1.05 times, the desired mechanical properties cannot be improved, and on the other hand, if it exceeds 2.00 times, the film will break due to a significant increase in stretching stress. In addition, if the heat treatment temperature during heat setting is less than 160°C, sufficient thermal stability cannot be obtained and the product cannot be used.
If it exceeds 50''C, the degree of crystallinity increases significantly, leading to a decrease in the abrasion resistance of the film, which is not preferable for use as a base film for magnetic tape.

In addition, after the completion of the above heat setting treatment, the above film is heated to a temperature of 100 to 160 °C, preferably 100 to 150 °C, and subjected to a relaxation treatment of 0.1 to 1% in the longitudinal direction to improve dimensional stability. This can be further improved.

The present invention will be explained below with reference to Examples.

In addition, the stress (F
-5 value) and heat shrinkage rate were respectively determined by the following measuring methods.

F-5 value: A rectangular sample with a width of 10M and a length of 15011IIg was cut parallel to the length and width directions of the film, and a tensile test was performed at a deformation rate of 100% per minute using a Tensilon manufactured by Toyo Baldwin. The stress at the time of 5% elongation was determined.

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

(Examples 1 to 5) The raw materials were dried polyethylene 2.6-naphthalate pellets (8) having an intrinsic viscosity of 0.55 and polyethylene terephthalate pellets (B) having an intrinsic viscosity of 0.62. A co-extruder in which two extrusion barrels are connected to one T-shaped die is used, with the inner layer being the raw material (B) and both outer layers being the raw material (B).
It was extruded to form a three-layer structure (^) and immediately cooled and solidified on a smooth drum to obtain an unoriented film with a thickness of 160 μm.

The unoriented film was stretched 3.2 times in the transverse direction at a temperature of 130"C, and then stretched 4.5 times in the machine direction at a temperature of 140"C to obtain a biaxially oriented film. The axially oriented film was further longitudinally stretched at a stretching ratio of 1.24 times at a temperature of 160''C, heat-set at 240°C for 2 seconds, cooled, and wound up.

The film is a layered film with a thickness of 10 μm, of which the inner layer is 8 μm thick and the outer layer is 1 μm thick. The physical properties and evaluation results of the film are shown in Table 1 (Example 1). Films were formed in the same manner as in Example 1, except that the inner layer was 6μ and the outer layer was 2μ. The physical properties and evaluation results of the film are shown in Table 1 (Example 2). Further, a film with an inner layer of 4 μm and an outer layer of 3 μm was formed in the same manner. The physical properties and evaluation results of the obtained film are shown in Table 1 (Example 3) Next, a film was formed in the same manner as in Example 3 except that the longitudinal re-stretching ratio was changed to 1.07 times. (thickness 10μ, Example 4
). In addition, a film was formed in the same manner as in Example 4, except that the longitudinal re-stretching ratio was 1.16 times, and the physical properties of the obtained film were as follows:
The evaluation results are shown in Table 1 (thickness lOμ.

Example 5).

(Comparative Examples 1 to 4) An unoriented film was obtained by melt-extruding polyethylene terephthalate raw material (B) in the same manner as in Example 1, and the film was stretched 3.2 times in the transverse direction at a temperature of 90°C, and then stretched at 95°C. The film was stretched 4.5 times in the machine direction at a temperature of 130° C. to form a biaxially oriented film, and further stretched at a temperature of 130° C. in the machine direction at a stretching ratio of 1.
The film was re-stretched by a factor of 24, heat set at 210° C. for 2 seconds, cooled, and wound to obtain a film with a thickness of 10 μm (Comparative Example 1).

Further, an unoriented film with a thickness of 160 μm obtained in the same manner as in Example 3 was subjected to horizontal and longitudinal stretching using conventional methods to obtain a final thickness of 10 μm.
A film of μ was produced. That is, the above-mentioned unoriented film was stretched 3.2 times in the transverse direction at 130°C, and then stretched at 140°C.
A biaxially oriented film was obtained by stretching 5.2 times in the longitudinal direction at 240° C., which was then heat-set at 240° C. for 2 seconds, cooled, and wound up (Comparative Example 2).

2).

(Comparative Examples 3 to 4) Comparative Example 3 was obtained by forming a film in the same manner as in Example 3 except that both longitudinal and transverse stretching temperatures were set to 180°C, and
Comparative Example 4 was obtained by forming a film in the same manner except that the transverse stretching ratio was 5.6 times.

The manufacturing conditions and performance of Examples 1 to 5 and Comparative Examples 1 to 4 are summarized in Table 1.

As is clear from comparing Examples 1 to 3 in the table above, the thicker the polyethylene 2.6-naphthalate layer, the more
The stress increases at 5% elongation, and conversely, the heat shrinkage rate at 105°C decreases.

Comparative Example 1 is an example of polyethylene terephthalate,
Examples are superior in both strength and heat shrinkage.

In Comparative Example 2, although the total longitudinal stretching ratio was the same as in Example 5, there were many breaks during film formation, and no product was obtained.

Comparative Example 3 and Comparative Example 4 both had stretching temperatures and stretching ratios that were outside the scope of the claims of the present invention, and products could not be obtained in both cases.

Margins below (Effects of the Invention) In the present invention, when producing a composite film using polyethylene terephthalate and polyethylene 2,6-naphthalate, a film laminated by a coextrusion method is stretched horizontally and longitudinally, and then stretched again longitudinally, This method also specifies the conditions for film formation, which significantly reduces breakage during film formation compared to the conventional horizontal and longitudinal stretching methods, enables smooth operation, and provides uniform quality, high strength, and heat resistance. A film with excellent properties can be obtained.

Claims (1)

[Claims] A substantially unoriented film obtained by laminating a film containing polyethylene terephthalate as a main component and a film containing polyethylene 2,6-naphthalate as a main component using a coextrusion method is heated at 100 to 170°C in the horizontal and vertical directions in that order. The film is sequentially stretched 2.5 to 5.5 times at a temperature of
．． A method for producing a composite film, which is re-stretched to 0.00 times and heat-set at 160 to 250°C.