JP2002273779A - Film manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film manufacturing device which makes a high speed manufacture possible without spoiling the quality of the film. SOLUTION: A main electrode 3 which applies static electricity to a film and an auxiliary electrode 5 which is grounded are arranged on the top of a section wherein the film S formed of a resin is first brought into contact with a carrying roll. In this case, the auxiliary electrode 5 is formed in a manner to cover and surround the opposite side from the film facing side of the main electrode 3. At the same time, the covering angle θ to the main electrode 3 is set to be in a range of 110 to 240 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film manufacturing apparatus using an electrostatic application method, and more particularly, to a film manufacturing apparatus capable of high-speed manufacturing without deteriorating film quality.

[0002]

2. Description of the Related Art In general, a resin film is produced by extruding a molten resin into a sheet from a slit die, cooling and solidifying the resin with a cooling roll, and then stretching the film uniaxially or biaxially. The resin films produced in this way are used in many applications, such as electrical component materials such as capacitors, magnetic materials such as magnetic recording tapes, and packaging materials. All applications require uniform thickness. Have been.

In order to fulfill such demands, one of the important factors when transporting a film by the above-mentioned film production apparatus is whether or not the film has sufficient adhesion to a transport roll. In particular, when the molten resin is extruded from the slit die and brought into contact with the cooling roll, if the adhesion is insufficient, the molding accuracy is deteriorated and the thickness uniformity is reduced.

Conventionally, as a countermeasure against the above-mentioned problem, when a molten film discharged from a slit die is cooled and solidified by a cooling roll, a high voltage is applied to an upper surface side of a portion where the film lands on the cooling roll surface. 2. Description of the Related Art There is known an electrostatic application method in which a wire-like electrode is disposed so as to traverse the electrode, static electricity is applied to the film from the electrode, and the adhesion to a cooling roll surface is electrostatically improved.

However, this electrostatic application method is effective in improving the adhesion of the film up to a certain molding speed.
When the forming speed is increased to improve productivity, air becomes caught between the film and the cooling roll, so that uniformity in thickness cannot be obtained and a limit is generated. For example, if the applied voltage is increased or the electrode is brought closer to the film to improve the adhesion between the film and the cooling roll, a breakdown occurs in the air layer between the electrode and the film, and a spark discharge occurs. This causes damage to the film and the surface of the cooling roll.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the conventional film manufacturing apparatus using the electrostatic application method, and to realize a high-speed film manufacturing without deteriorating the quality of the film. It is to provide a device.

[0007]

According to the present invention, there is provided a film manufacturing apparatus comprising: a main electrode for applying static electricity to a film formed of a resin; A grounded auxiliary electrode is disposed, the auxiliary electrode is formed so as to cover the side surface of the main electrode opposite to the film facing side, and the covering angle θ with respect to the main electrode is in the range of 110 ° to 240 °. It is characterized by having made it.

As described above, with respect to the main electrode which acts to apply static electricity to the film, a grounded auxiliary electrode is provided at a position opposite to the film with respect to the main electrode so as to cover the main electrode. And setting the covering angle θ of the auxiliary electrode in the range of 110 ° to 240 °, the charge density applied to the film can be efficiently improved. Due to the improvement in the charge density, even when the film is transported at a high speed, it is possible to maintain the adhesiveness to the transport roll and to produce a film having excellent thickness uniformity.

[0009] The adhesion of the film is particularly high when the volume resistivity of the auxiliary electrode facing the main electrode is 10 ⁵ to 1.
It becomes more remarkable when it is made of a material of 0 ¹⁵ Ωcm, and it is particularly preferable to use ceramics. Here, the volume resistivity is
It is defined by the measurement method specified in JIS K-6911. Further, as the ceramics, those having a large number of pores are preferable. Particularly, the use of chemically bonded ceramics can further improve the performance.

Since the electric resistance of the auxiliary electrode made of such a material is close to the electric resistance of the film, it is easier to make the auxiliary electrode closer to the main electrode while suppressing generation of spark discharge and charging of the auxiliary electrode. Thus, the electric field strength near the main electrode can be increased, and the adhesion of the film can be improved.

The above-mentioned action can be achieved in any transporting step in the film manufacturing apparatus, but can be remarkably exhibited particularly in the step of extruding the molten resin from a slit die and cooling and solidifying it with a cooling roll.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a thermoplastic resin is used as a resin constituting a film. For example,
Polyesters such as polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate and their copolymers, polyolefins such as polyethylene, polypropylene and their copolymers,
Examples thereof include polyamides such as nylon 6, nylon 66, nylon 12, and copolymers thereof. Among these, polyesters are particularly preferred,
Further, among polyesters, polyethylene terephthalate is preferred. If necessary, additives such as an antistatic agent, a weathering agent, a lubricant, and a pigment may be added to these resins.

The present invention can be applied to any process such as a molding process and a stretching process as long as the film is transported by a transport roll in a film manufacturing apparatus. This is very effective when used in a molding step of extruding a molten film from a roll and bringing the molten film into contact with a cooling roll to cool and solidify the film.

In the film manufacturing apparatus of the present invention, an electrostatic applying means for applying static electricity to the film is provided above the vicinity of the portion where the film first comes into contact with the transport roll so as to extend in the width direction of the film. . In addition, a main electrode and a grounded auxiliary electrode are arranged as the electrostatic application means. The auxiliary electrode is arranged on the side opposite to the film with the main electrode interposed therebetween, and is formed so as to cover the outer periphery of the main electrode for substantially half the circumference and to open to the film side. The covering angle θ defined by the angle between both tangents drawn from both ends of the opening of the auxiliary electrode toward the film-facing surface of the main electrode is in the range of 110 ° to 240 °.

If the covering angle θ is smaller than 110 °, the electric charge generated between the main electrode and the auxiliary electrode is reduced, and the efficiency is deteriorated. Conversely, if the covering angle θ is larger than 240 °, although a large amount of charge is generated between the main electrode and the auxiliary electrode, most of the charge leaks to the auxiliary electrode side, so that the amount of charge that can be applied to the film is improved. Disappears. In particular, when ceramic is used for the auxiliary electrode, it is preferable to set the covering angle θ in the above range.

By adjusting the covering angle θ of the auxiliary electrode with respect to the main electrode in the range of 110 ° to 240 ° as described above, the charge generated between the main electrode and the auxiliary electrode can be efficiently directed to the film. Thus, the adhesion between the film and the transport roll can be further improved. Therefore, even if the moving speed of the film is increased, the adhesion of the film can be maintained, and the production of a film having excellent thickness uniformity can be achieved.

The main electrode is not particularly limited in form, but is formed in a wire shape, a blade-shaped cross-section, or an elliptical cross-section. In either case, the material used is a conductive metal or carbon.
Metals include stainless steel, titanium, beryllium copper,
Palladium, permalloy, tantalum, gold, platinum, silver,
Examples thereof include copper, brass, iron, tin, aluminum, nickel, zinc, molybdenum, and tungsten.

As described above, the auxiliary electrode is formed in a semi-cylindrical shape such as a half-cylinder or a half-square tube that covers substantially half of the outer periphery of the main electrode. In the semi-cylindrical shape, the inner wall side facing the main electrode is made of a material having a volume resistivity of 10 ⁵ to 10 ¹⁵ Ωcm, and the outer wall side is made of the same conductive metal or carbon as the main electrode. , So that the part is grounded.

When the volume resistivity is smaller than 10 ⁵ Ωcm, the current leaking to the auxiliary electrode side is too large, and the efficiency is deteriorated. On the other hand, when the volume resistivity is larger than 10 ¹⁵ Ωcm, almost no current leaks to the auxiliary electrode side, so that the auxiliary electrode is charged and the potential difference changes, and as a result, the adhesion is not improved. That is, when the inner wall side is made of the material having the above volume resistivity, the charge generated between the main electrode and the auxiliary electrode can be more efficiently directed to the film. As this material, ceramics is preferable, and more preferably, chemically bonded ceramics not subjected to sintering is used. In particular, it is preferable to use a non-sintered chemically bonded ceramic containing an inorganic binder, an inorganic auxiliary fiber, and an inorganic filler.

The electrode portion of the auxiliary electrode may be formed so as to cover the outer peripheral side of the above material with a conductive material, or may be formed by spraying a metal such as aluminum or molybdenum. By configuring the outer wall portion of the auxiliary electrode with these materials and grounding, it becomes possible to stably leak a part of the electric charge generated between the main electrode and the auxiliary electrode to the auxiliary electrode side,
Completely prevent the charging of the auxiliary electrode, bring the auxiliary electrode close to the main electrode or increase the covering angle θ while keeping the potential difference with the main electrode constant, and efficiently increase the amount of electrostatic charge applied to the film. , And can be improved stably.

FIGS. 1 and 2 exemplify a case where the film manufacturing apparatus of the present invention is applied to a forming step.

Reference numeral 1 denotes a slit die, which extrudes a molten resin into the shape of a film S from a die lip 1a at the lower end, and contacts a surface of a cooling roll 2 rotating in the direction of an arrow to solidify by cooling. The slit die 1 is not particularly limited as long as it has a slit-shaped discharge port. For example, T-die,
A coat hanger die, a fish tail die and the like can be used. The film cooled and solidified by the cooling roll 2 is subsequently sent to a stretching step (not shown), where it is sequentially or simultaneously stretched uniaxially or biaxially in the machine direction or the machine direction to be formed into a stretched film.

On the upper side of the portion where the film S in the molten state first lands on the cooling roll 2, a wire-shaped main electrode 3 for applying electrostatic force is applied to the film S so as to cross the film S in the width direction. mm to several tens of mm. Several kV to several tens k from a power supply (not shown)
Since a DC voltage of V is applied, static electricity is applied to the film S so that the film S is brought into close electrostatic contact with the surface of the cooling drum 2. The voltage applied here may be either a positive voltage or a negative voltage.

Both ends of the main electrode 3 extending in the width direction of the film S are covered with insulating materials 4 and 4, respectively.
These insulating materials 4 and 4 are respectively provided so as to slightly overlap both ends in the width direction of the film S, and the overlap prevents spark discharge from being generated from the main electrode 3 to the cooling roll 2.

Further, a semi-cylindrical auxiliary electrode 5 is provided around the main electrode 3 so as to surround the outside on the side opposite to the film facing side. This semi-cylindrical auxiliary electrode 5 has 2
The inner layer 5a facing the main electrode 3 is made of a non-conductive ceramic, and the outer layer 5b
Is made of conductive metal or carbon and is grounded. The auxiliary electrode 5 has an angle θ sandwiched between two tangents drawn from both ends a and b of the opening toward the film facing side of the main electrode 3, that is, a covering angle θ of 110 ° to 240 °.
° is set to be in the range.

In the film manufacturing apparatus of the present invention, it is more preferable to change the setting as follows, particularly when the main electrode 3 has a circular cross section and a blade cross section.

In the case where the main electrode is in the form of a wire having a circular cross section, as shown in FIG.
The covering angle θ surrounding the opposite side of the film facing side may be 110 ° to 240 ° as described above, preferably 150 ° to 240 °, more preferably 170 ° to
It is good to set it in the range of 220 °. Further, the shortest distance L2 from the opening ends a and b of the semi-cylindrical auxiliary electrode 5 to the wire-shaped main electrode 3 and the shortest distance L1 from the main electrode 3 to the film S
And L2 ≦ L1.

In the case where the main electrode 3 has a blade-shaped cross section, as shown in FIG. 4, from the opening ends a and b of the semi-cylindrical auxiliary electrode 5 to the ends of the main electrode 3 on the film facing side, respectively. Angle θ between two drawn tangents, that is, covering angle θ
May be 110 ° to 240 °, preferably 11
0 ° to 200 °, more preferably 160 ° to 18 °
It is good to be 0 °. The shortest distance L4 from both ends a and b of the opening of the semi-cylindrical auxiliary electrode 5 to the film-side end surface of the main electrode 3 and the shortest distance L3 from the film-side end surface of the main electrode 3 to the film S are L4. It is preferable that the relationship of L3 is satisfied. Further, it is preferable that the shortest distance L4 be substantially equal to the shortest distance L5 from the end face of the main electrode 3 opposite to the film facing side to the inner face of the auxiliary electrode 5.

In the present invention, the preferable range of the covering angle θ of the auxiliary electrode with respect to the main electrode as described above is shifted depending on the shape of the main electrode, depending on the shape of the electric field generated by application from the main electrode. . Therefore, if the covering angle θ is optimized according to the shape of the main electrode, the most efficient electrostatic application can be realized.

Here, the auxiliary electrode may be provided over the entire width in the width direction of the film S, or may be provided locally.

Further, the additive formed in the semi-cylindrical shape as described above is liable to adhere and deposit an additive contained in the raw material resin and a product generated by thermal decomposition of a part of the resin.
Such adhesion and deposition of the product can be prevented by providing a heating means such as embedding a heater in the auxiliary electrode.

[0032]

EXAMPLES Examples and comparative examples will be described below. The meanings of the evaluations used in these examples and comparative examples are as follows.

[Upper limit speed] The upper limit speed refers to the rotation speed of the cooling roll at a limit at which air entrapment, which occurs when the adhesion between the film and the cooling roll is insufficient, does not occur.

[Thickness unevenness] It is a fluctuation rate calculated from the maximum value and the minimum value of the thickness of the unstretched film on the cooling roll in the longitudinal direction of 1 m by the following formula.

Variation (%) = ｛(maximum thickness−minimum thickness)
/ Average thickness｝ × 100 Examples 1 to 5, Comparative Example 1 Orthochlorophenol intrinsic viscosity at 25 ° C. is 0.615
The polyethylene terephthalate was melted at 280 ° C. and extruded using the manufacturing apparatus shown in FIGS. 1 and 2 under the following conditions to produce a film having an average thickness of 0.1 mm. Was varied as shown in Table 1 (Examples 1 to 5). As Comparative Example 1, a film having an average thickness of 0.1 mm was manufactured under the same conditions as in Examples 1 to 5 except that no auxiliary electrode was provided.

Table 1 shows the results of measuring the upper limit speed of the cooling roll and the thickness unevenness when the speed of the cooling roll was set to 40 m / min and 60 m / min for the above six levels.
It was shown to.

Die lip: width = 400 mm, slit gap = 2.5 mm Main electrode: stainless steel wire (diameter = 0.1 mm) Auxiliary electrode: shape = half cylindrical shape (FIG. 3), inner layer = chemical bonding ceramics (Nichias ( 3. Neo-Arc Co., Ltd., volume resistivity = 10 ¹³ Ωcm), outer layer = sprayed layer of molybdenum Distance between die lip and film: 30 mm Minimum distance between main electrode and film: 5 mm Minimum distance between main electrode and auxiliary electrode: 5mm Applied voltage (DC): 10kV

[0038]

[Table 1]

Examples 6 to 10 and Comparative Example 2 Resins having an average thickness of 0.1 mm were prepared in the same manner as in Examples 1 to 5 except that the conditions of the main electrode / auxiliary electrode were changed as follows. In manufacturing the film, the covering angle θ of the auxiliary electrode with respect to the main electrode was varied as shown in Table 2 (Examples 6 to 10). As Comparative Example 2, a film having an average thickness of 0.1 mm was manufactured under the same conditions as in Examples 6 to 10 except that no auxiliary electrode was provided.

Table 2 shows the results of measuring the upper limit speed of the cooling roll and the thickness unevenness when the speed of the cooling roll was set to 40 m / min and 60 m / min for the above six levels.
It was shown to.

Main electrode: stainless steel blade (width =
8 mm, thickness = 50 μm) Auxiliary electrode: Shape = Combination of semicircle and rectangle (Fig. 4)
Inner layer = Chemically bonded ceramics (Neoarc Co., Ltd., Neoarc, volume resistivity = 10 ¹³ Ωcm), Outer layer = Sprayed layer of molybdenum Distance between film end face of main electrode and film: 5 mm Shortest distance between main electrode and auxiliary electrode : 3 mm Shortest distance from the opposite side of the film side end surface of the main electrode to the auxiliary electrode: 3 mm Applied voltage (DC): 9 kV

[0042]

[Table 2]

[0043]

As described above, according to the present invention,
With respect to the main electrode that acts to apply static electricity to the film, a grounded auxiliary electrode is disposed at a position opposite to the film with the main electrode interposed therebetween so as to cover the main electrode, and the auxiliary electrode By setting the covering angle θ in the range of 110 ° to 240 °, the charge density applied to the film can be efficiently improved. Due to the improvement in the charge density, even when the film is transported at a high speed, it is possible to maintain the adhesiveness to the transport roll and to produce a film having excellent thickness uniformity.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a main part of an example of a film manufacturing apparatus of the present invention.

FIG. 2 is a schematic front view of the film manufacturing apparatus of FIG.

FIG. 3 is a schematic side view showing an electrode portion of the film manufacturing apparatus of the present invention.

FIG. 4 is a schematic side view showing another example of the electrode portion of the film manufacturing apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 1 slit die 1a die lip 2 cooling roll 3 main electrode 5 auxiliary electrode 5a inner layer (ceramics) 5b outer layer (electrode part) S film θ covering angle

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hidetoshi Okagi 1-1-1 Sonoyama, Otsu-shi, Shiga F-term in the Shiga Plant of Toray Industries (reference) 4F207 AA25 AG01 KA01 KE06 KK66 KM06 KM16 KW23 KW50

Claims (10)

[Claims] 1. A main electrode for applying static electricity to a film and a grounded auxiliary electrode are arranged above a portion where a film formed of resin is first brought into contact with a transport roll, and the auxiliary electrode is connected to the main electrode. A film manufacturing apparatus which is formed so as to cover the side surface on the side opposite to the film facing side and has a covering angle θ of 110 ° to 240 ° with respect to the main electrode. 2. The film manufacturing apparatus according to claim 1, wherein the film is a molten film extruded from a slit die, and the transport roll is a cooling roll for cooling and solidifying the molten film. 3. The main electrode is formed in a wire shape, and a covering angle θ of the auxiliary electrode with respect to the main electrode is 150 ° or more.
The film manufacturing apparatus according to claim 1 or 2, wherein the angle is set to 240 °. 4. The film manufacturing apparatus according to claim 3, wherein the shortest distance L2 from the main electrode to the auxiliary electrode is in a relationship of L2 ≦ L1 with the shortest distance L1 from the main electrode to the film. 5. The main electrode is formed in a blade-shaped cross section,
And the covering angle θ of the auxiliary electrode with respect to the main electrode is 110
The film manufacturing apparatus according to claim 1 or 2, wherein the angle is set to? 6. The film according to claim 5, wherein the shortest distance L4 from the film facing surface of the main electrode to the auxiliary electrode is in a relationship of L4 ≦ L3 with the shortest distance L3 from the main electrode to the film. manufacturing device. 7. The film manufacturing apparatus according to claim 1, wherein a side of the auxiliary electrode facing the main electrode is made of a material having a volume resistivity of 10 ⁵ to 10 ¹⁵ Ωcm. 8. The film manufacturing apparatus according to claim 1, wherein a material of the auxiliary electrode facing the main electrode is ceramics. 9. The film manufacturing apparatus according to claim 8, wherein the ceramic is a chemically bonded ceramic. 10. A method for producing a film using the apparatus according to claim 1.