JPH07186253A - Apparatus for molding inflation film and film making method - Google Patents

Abstract

PURPOSE:To control effectively the generation of wrinkles and folding lines on a film by installing a means for transferring a sag generated in the film behind a guide member and then installing a folding means comprising rolls in front of the film. CONSTITUTION:In a method in which a ring-shaped film is formed by extruding a molten raw material resin such as an aromatic polyester, a gas is supplied into a inner space while being cooled, a cylindrical stretched film is formed, and the film is extracted through a guide member while being folded into a sheet form, a width spreading means 5 having a function for transferring a sag generated in a film 3 to the end of the film, e.g. an expanding roll 9, is installed behind a guide member 4, and then a folding means 6 comprising two or more rolls which are arranged not to come into contact with each other through the film is placed in front of the film 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inflation film forming apparatus and an inflation film forming method. In particular, the present invention relates to an inflation film molding apparatus and an inflation film molding method that produce an excellent effect described below when an aromatic polyester (hereinafter referred to as aromatic polyester) capable of forming an optically anisotropic melt is used as a raw material thermoplastic resin.

[0002]

2. Description of the Related Art Aromatic polyester films exhibit excellent properties such as mechanical strength, electrical properties, heat resistance, chemical resistance, and dimensional stability. Therefore, in particular in the electronic field, attention is focused on as an insulating material, a printed circuit board material, a laminated material, and the like, and in other fields, various applications in which heat resistance is required, such as heat resistant laminated material applications, are expected.

An inflation film molding method is one of the film molding methods. FIG. 2 schematically shows a conventional blown film molding apparatus. According to this, the raw material thermoplastic resin is the annular slit 1
Melt-extruded to form an annular film 2.
A gas such as air is supplied to the inner space of the annular film to be expanded by the inner pressure, and at the same time, the outer surface of the annular film is cooled to form the cylindrical stretched film 3. The cylindrical film 3 is gradually flattened by a guide member 4 such as a pair of guide plates (or guide rolls) that are inclined so that their downstream portions are close to each other. After that, it is further folded by the pair of rear nip rolls 7 and taken up. The nip rolls are composed of a pair and are usually a combination of a rubber roll and a metal roll. The roll has a pressing pressure (indicated by an arrow)
Thus, it has a function of folding the film into a sheet shape and taking it out, and a function of sealing the inner space gas (sealing 80% or more of the supply gas). After that, both ends of the folded film are cut open with a leather knife or the like and wound as two flat film-shaped films, or wound as it is as a bag-shaped film.

[0004]

By the way, when a resin having high rigidity such as aromatic polyester is molded by the conventional inflation film molding apparatus as described above, a flattened cylindrical shape is formed near the outlet of the guide member 4. Irregular sagging is seen in the center of the film 3, and a large number of irregular wrinkles and folds are observed immediately after passing through the nip rolls, and it is necessary to stably produce a flat film that can be used practically. I can't. It is presumed that this is because a film made of a resin such as aromatic polyester has a high elastic modulus. That is, folding of a rigid and rigid cylindrical film into a flat shape without wrinkles could not be easily achieved by a conventional inflation film molding apparatus or molding method.

In order to solve this drawback, for example, a heat retaining cylinder for retaining the heat of the cylindrical stretched film 3 is provided between the expansion start portion of the cylindrical stretched film 3 and the guide member 4 (Japanese Patent Laid-Open No. 4-53728). (Japanese Patent Laid-Open No. 4-286626) and a method in which a liquid bath is installed on the downstream side of the expanded cylindrical stretched film 3 to immerse the film (Japanese Patent Laid-Open No. 4-286626). However, these methods are limited to the case where the molten resin is extruded downward from the annular slit 1 to form the cylindrical film 3, and the application range is narrow.

An object of the present invention is to limit the extrusion direction of a molten raw material resin from an annular slit even when a resin which becomes a rigid and hard film such as an aromatic polyester film is used as a raw material resin in blown film molding. It is an object of the present invention to provide a film forming apparatus and a film forming method capable of effectively suppressing the generation of wrinkles and creases in the obtained film.

[0007]

[Means for Solving the Problems] The above object is to melt-extrude a raw material resin to form an annular film, and while cooling the annular film, supply gas to the inner space of the annular film to expand it by an internal pressure so as to expand it into a cylindrical shape. In an inflation film forming apparatus that forms a film and pulls the cylindrical film through a guide member while folding it into a sheet shape, the slackening that occurs on the film is moved to the end of the film behind the guide member. Inflation characterized by arranging a means (for example, an expander roll) and a folding means formed of two or more rolls which are arranged so as not to alternate with the film sandwiching the film in the advancing direction of the film. It can be achieved by a film forming apparatus and a film forming method using the above apparatus. INDUSTRIAL APPLICABILITY The apparatus and method of the present invention can exert an excellent effect particularly in inflation film molding of a rigid and hard film such as an aromatic polyester film.

In the blown film forming apparatus and film forming method of the present invention, the folding of the film and the sealing of the inner space gas, which are conventionally performed by the nip rolls, are arranged so as not to come into contact with the widening means and subsequently. It is characterized by using more than one roll.

[0009]

The widening means is a means for moving the slack generated on the film to the end of the film, and is located behind the guide member. In the vicinity of the exit of the guide member, slack is irregularly generated on the flattened cylindrical film. It is considered that this slack causes wrinkles and creases in the obtained film. Therefore, if this slack can be moved to the edge of the film, it is considered that a film free from wrinkles and creases can be obtained. As widening means,
For example, there are ordinary expander rolls, tenter rolls, and the like, and if necessary, suitable guide plates or guide rolls may be combined. A tenter may be used as the widening means. After passing through the guide member, the film that has passed through the widening means is composed of the following two or more rolls, with the slack of the film being moved to the end, and at least the center of the film having no slack. You can proceed to.

Behind the widening means is a folding means which is composed of two or more rolls positioned so as not to contact each other. This further folds the film and seals the inner space gas. The rolls are arranged so as not to alternately contact each other with the film sandwiched therebetween in the traveling direction of the film. The flat film that has advanced from the widening means is advanced in an S shape through two or more rolls. The contact length (angle of wrap) between the roll and the film is sufficiently taken to provide frictional resistance that prevents the film and the roll from slipping. Furthermore, by providing a speed difference between the adjacent rolls, the film Appropriate tension can be applied. By adopting such a mechanism, it becomes possible to fold the cylindrical film and to have a function of sealing the gas in the inner space without using a nip roll.

For example, when using two rolls,
The diameter of the roll must be increased in order to increase the contact length between the roll and the film, but a roll having a diameter of at least 10 cm is preferable for practical use. By increasing the number of rolls, it is possible to increase the contact length between the whole roll and the film, so the roll diameter can be smaller than 10 cm, and it is also possible to give tension to the film by arranging the rolls. is there. Since the effect of the present invention is more remarkably exhibited, it is preferable that the means for using two or more rolls of the present invention has a driving device attached to at least one or more rolls for taking up the film.
Further, as the material of the roll, as long as it can impart an appropriate frictional resistance, either metal or rubber can be used, but rubber is preferable.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the device or method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an embodiment of the blown film molding apparatus of the present invention, and shows a case where a melt of a raw material aromatic polyester is extruded upward from an annular slit 1 of an extruder. The aromatic polyester melt-extruded upward from the annular slit 1 forms an annular film 2, which is expanded by internal pressure when a gas such as air is supplied to the inner space, and at the same time the outer surface is expanded. Is cooled to form a cylindrical stretched film 3. The film is guided by the guide member 4.
It gradually folds flat. Next, the slack of the stretched film is guided to the widening means 5 located behind the guide member 4 and transferred to the end portion. Next, 2 which constitutes the folding part 6
With more than one roll, the film is folded and the gas in the cylinder is sealed to obtain a flatly folded film. FIG. 1 shows an example in which the guide member 4 is composed of an inverted V-shaped guide plate, and the folding portion 6 is composed of three rolls. The film tension is adjusted by adjusting the position of the central roll or by imparting a minute difference in the driving speed of the three rolls. Although not shown in the figure, thereafter, both ends of the film may be slit by a conventional method with a leather knife or the like to remove the folds, and two flat film-shaped films may be wound up by a take-up machine.

FIG. 3 is a detailed view of an example of the widening portion 5, which is a view of FIG. 1 as viewed from the left side. The widening section 5 is composed of at least one guide roll 10 and 11 and at least one expander roll 9. The pair of guide plates 8 is a flat film 12 which is still incompletely folded.
It consists of two plates with a length of 3 cm or more having a gap (usually 0.5 to 10 mm) larger than the thickness of the two films to be passed through. As a guide plate for more effectively operating the widening function, it may be attached if necessary.
The widening is performed by the expander roll 9, and the slack of the film is transferred to both ends by rotating the bow-shaped expander roll while contacting the film surface. In FIG. 3, the slack on one side of the film (upper side of the paper surface) is mainly transferred to both ends, but similarly the slack on the other side, which does not come into contact with the expander roll, is taken on the other side to take slack. Even better with a roll attached.

In FIG. 4 as well, similar to FIG. 3, another example of the widening portion 5 is shown.
FIG. The tenter roll 13 is composed of a total of four (2 pairs) rolls, two rolls (one pair) sandwiching the end portion of the film being arranged at both ends of the film, and guides before and after the rolls. An example in which the rolls 14 and 15 are attached to one side is shown. Two pairs of rotating rolls 1
By adjusting the angle of 3, the slack of the film can be moved to the end.

In the present invention, it is essential that the widening means is arranged in front of the folding means instead of the nip rolls, and the folding means is composed of two or more rolls adjacent to each other. That is, when only the folding means is composed of two or more rolls adjacent to each other and no widening means is provided,
When a general nip roll is used with only a means having a widening function provided behind the guide member, the film has many wrinkles and creases as in the conventional case. In order to form a flat aromatic polyester film with few wrinkles and creases, a means with a widening function instead of a nip roll and a means for folding the film with two or more rolls and sealing the inner space gas are also used. It becomes effective for the first time.

The aromatic polyester capable of forming an optically anisotropic melt, which can be used in the film forming apparatus and the forming method of the present invention, includes aromatic diols, aromatic dicarboxylic acids and aromatic hydroxycarboxylic acids. It is a polyester containing at least one component and exhibits optical anisotropy in the melt phase. Such characteristics can be easily identified by heating and melting the sample placed on the hot stage in a nitrogen atmosphere and observing the transmitted light with a polarizing microscope. Further, the aromatic polyester may be blended with an antioxidant, an ultraviolet absorber, an antistatic agent, a foaming agent, a flame retardant, a coloring agent, a lubricant, etc. within a range that does not impair the formation of the optically anisotropic melt. Good.

In the present invention, not only the rigid aromatic polyester film but also other general non-rigid polyethylene film, polypropylene film and the like are effective for preventing wrinkles and creases. Appears significantly.

Hereinafter, the present invention will be described in more detail with reference to examples, but it goes without saying that the present invention is not limited to the examples. Example 1 An inflation film was manufactured using an apparatus as shown in FIG. As a raw material, repeating unit [1]

[0019]

[Chemical 1]

And repeating unit [2]

[0021]

[Chemical 2]

A pellet of aromatic polyester (VECTRA A900F, manufactured by Hoechst Celanese), which is composed of and has the property of forming an optically anisotropic melt, is preheated at a temperature of 150 ° C. for 6 hours, and a 40 mmφ extruder is used. Was melt-extruded at 280 ° C. and discharged from an annular slit having a diameter of 25 mmφ (gap: 0.6 mm) to form an annular film. While cooling the outer surface of this annular film, air was supplied to the inner space and expanded by the inner pressure to form a cylindrical stretched film. A widening part and 3 behind the guide member
A folding part composed of individual rolls was provided to form a folded film. Then, both ends of the folded film were slit and taken out. On this occasion,
As the widening section, the guide plate, expander roll and guide roll shown in FIG. 3 were used. The three rolls instead of the nip rolls were rubber rolls each having a diameter of 8 cm, and the two rolls except the central roll were 6.0 m / min and 6.02 m / min, respectively.
A take-up function was provided by driving and rotating at a surface speed of a minute. The center roll was a position-moving type tension adjusting roll that rotated in contact with the film and did not have a drive unit. The film tension at this time is 0.02k
It was g / cm, but there was no slip between the film and the roll,
The air in the cylindrical film could be sealed.

The moldability of the obtained film was judged according to the following criteria. Wrinkles, creases: number of creases, creases per unit area visually observed in the obtained film (pieces / m ² ) Stability: fluctuation of expanded cylindrical stretched film, diameter variation A, B, and C were ranked to indicate stability during molding. A: Fluctuation, almost no change is visible. B: Fluctuations and fluctuations are visible. C: Fluctuations and fluctuations appear large. The results are shown in Table 1.

Example 2 The widening means shown in FIG. 4 was used in place of the widening means shown in FIG. 3, and two rubber rolls having a diameter of 15 cm for passing the film in an S-shape were used as folding parts of the film. A film was formed by the same procedure as in Example 1. 2 of FIG.
The pair of tentering rolls (total of 4 rolls) had a diameter of 6.5 cm, and were freely rotated in the film advancing direction at an angle of 45 degrees without driving. The two rolls in the folding portion were independently driven and rotated at a surface roll speed of 10 m / min. The air inside the cylindrical film could be sealed without slippage of the film and roll appearance. The results of the film formability are shown in Table 1.
Shown in.

Comparative Example 1 A film was formed in the same manner as in Example 1 except that the apparatus shown in FIG. 2 was used instead of the apparatus shown in FIG. The results of the film formability are shown in Table 1.

Comparative Example 2 A film was formed by the same procedure as in Example 1 except that the widening means shown in FIG. 3 was not used. The results of the film formability are shown in Table 1.

Comparative Example 3 As a folding part, the film is passed in an S-shape 2
A film was formed by the same procedure as in Example 2 except that a nip roll was used instead of the rubber roll having a diameter of 15 cm. The results of the film formability are shown in Table 1.

[0028]

[Table 1]

[0029]

According to the present invention, it is possible to effectively eliminate the slack on the film that occurs in the blown film forming step, and therefore it is possible to form a film having no wrinkles or creases. Furthermore, according to the present invention, it is extremely stable and smooth to squeeze the cylindrical film flatly,
Pressure fluctuation of seal gas used for expansion molding is reduced,
As a result, the film is uniformly expanded, the fluctuation of the diameter of the cylindrical film is reduced, and a flat film can be stably obtained. The effect can be particularly remarkably exhibited in the inflation film molding of a rigid film such as an aromatic polyester film.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an inflation film molding apparatus of the present invention.

FIG. 2 is a view showing an embodiment of a conventional blown film molding apparatus.

FIG. 3 is a diagram showing an embodiment of a widening means constituting the film forming apparatus of the present invention.

FIG. 4 is a diagram showing another embodiment of the widening means constituting the film forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Annular slit 2 Annular film 3 Cylindrical stretched film 4 Guide member 5 Widening part 6 Folding part 7 Nip roll 8 Guide plate 9 Expander roll 10, 11 Guide roll 12 Film 13 Width roll 14, 14 Guide roll

Claims (4)

[Claims] 1. A raw material resin is melt-extruded to form an annular film, and a gas is supplied to the inner space of the annular film while cooling the annular film to expand it by an internal pressure to form a cylindrical stretched film. In the inflation film forming apparatus that draws the cylindrical film through while folding it into a sheet shape, behind the guide member, a widening means having a function of moving the slack generated on the film to the film end portion, and subsequently, the film widening means. An inflation film forming apparatus, characterized in that a folding means composed of two or more rolls arranged so as not to alternately contact with the film sandwiched in the traveling direction is arranged. 2. The molding apparatus according to claim 1, wherein the raw material resin is an aromatic polyester capable of forming an optically anisotropic melt. 3. A raw material resin is melt-extruded to form an annular film, and while the annular film is cooled, gas is supplied to the inner space of the annular film to expand it by an internal pressure to form a cylindrical stretched film. In the inflation film molding method, in which the cylindrical film is drawn while folding it into a sheet, the film that has passed through the guide member is passed through a widening means having the function of moving the slack generated on the film to the film end, The film forming method is characterized in that the film is passed through a folding means composed of two or more rolls which are arranged so as not to alternately contact with each other with the film sandwiched therebetween in the traveling direction of the film. 4. The molding method according to claim 3, wherein the raw material resin is an aromatic polyester capable of forming an optically anisotropic melt.