JPH03147828A - Wire electrode for electrostatic application cooling method of thermoplastic resin sheet - Google Patents

Abstract

PURPOSE:To strengthen electrostatic adhesion and improve the manufacturing speed by having characteristics in which electrode is 80mum or less in wire diameter and consisting of a metal or alloy of amolphous and an electric discharge phenomenon never that looks like beads occurs on the wire surface in the case when negative voltage is applied and discharged in a tension applied condition. CONSTITUTION:It is necessary that a wire electrode is 80mum or less in wire diameter (diameter), preferably 60mum or less. In a wire electrode which exceeds 80mum in wire diameter, an improved effect is seldom recognized in an electrostatic adhesion. And, in the case when negative voltage is applied and discharged in a tension applied condition, it has character in which an electric discharge phenomenon that looks like beads never occurs on the wire surface. As the negative voltage mentioned above, about 6kV or more is employed and as the tension, about 600g weight or more (namely, 300kg per unit area (mm<2>)) is employed. The above-mentioned discharge phenomenon takes place in a dark room.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wire electrode of a thermoplastic resin sheet based on the electrostatic application cooling law. This article relates to a wire electrode according to the electrostatic application cooling law, which is used when attaching an electrostatic charge to a resin sheet using a wire electrode and bringing the resin sheet into close contact with a rotating cooling body.

[Prior art and problems to be solved by the invention] Among thermoplastic resins, polyester films, especially polyethylene terephthalate films, have excellent mechanical properties, electrical properties, chemical resistance, dimensional stability, etc. Because of this, it is used as a base material in many fields such as magnetic tape, capacitors, packaging, plate making, electrical disconnection, and photographic film.

Incidentally, in recent years, requirements for film quality have become increasingly strict, and in particular, improving thickness accuracy has become an indispensable condition.

A method of forming a thermoplastic resin into a film by melt extrusion molding involves cooling and solidifying a molten resin sheet extruded from a die into a sheet shape on a rotating cooling body, and then stretching the obtained resin sheet. However, it is known that the thickness unevenness of the film is significantly affected by the state of cooling and solidification of the molten resin sheet on the rotary cooling body.

To improve the thickness unevenness of the film, for example,
As described in Publication No. 7-6142, it is known that the so-called electrostatic application cooling method, which applies an electrostatic charge to the surface of a molten resin sheet and brings the resin sheet into close contact with the surface of a rotating cooling body, is effective. Widely used industrially.

However, in this electrostatic cooling method, when the speed of the rotary cooling body is increased for the purpose of increasing productivity, the adhesion between the molten resin sheet and the rotary cooling body decreases, resulting in the formation of so-called bound bubbles. However, this is not acceptable as a quality characteristic required for the product.

In order to solve the above problems, for example,
No. 8262, JP-A-54-34370, and JP-A-5
Various methods have been proposed, such as in No. 6-53037. These methods include irradiating the wire electrode with infrared rays, bringing another grounded cover-like electrode close to the electrode, and using a plate-like electrode with a curved end, but none of them are effective. However, there are disadvantages such as the fact that the amount of energy is small, or even if it is effective, the device is large-scale and difficult to install.

On the other hand, when using wire electrodes, the easiest way to increase the adhesion between the molten resin sheet and the rotating cooling body is to reduce the wire diameter.

However, as the wire diameter decreases, the tensile strength at break decreases, making it easier to break, so it is necessary to lower the tension of the wire electrode, but this would cause the wire itself to vibrate due to ionic wind and machine vibration. As a result, the film becomes uneven, the commercial value of the film is lost, and spark discharge becomes more likely to occur, which impedes stable operation.

Conventionally, tungsten wires have been mainly used as wire electrodes, but for the reasons mentioned above, the practical limit for the wire diameter is about 80 μm.

Due to the above circumstances, even in the electrostatic application cooling method,
The current situation is that the speed of the rotary cooling body cannot be increased sufficiently.

[Means for solving problems]

As a result of intensive studies in view of the above circumstances, the inventors of the present invention found that a wire having certain characteristics can adhere the molten resin sheet well even when the speed of the rotary cooling body is increased.
The present invention has been completed.

That is, the gist of the present invention is a wire electrode used when applying an electrostatic charge to a molten thermoplastic resin extruded in a sheet form from a gou using a wire electrode, and bringing the resin sheet into close contact with a rotating cooling body. The wire electrode has a wire diameter of 80 μm or less, is made of an amorphous metal or alloy, and does not exhibit a bead-like discharge phenomenon on the wire surface when a negative voltage is applied and discharged under tension. An electrostatic applied cooling law wire electrode of a thermoplastic resin sheet is characterized by having the following characteristics.

The present invention will be explained in detail below.

The electrostatic applied cooling law wire electrode of the present invention is comprised of an amorphous metal or alloy. Amorphous alloys are more desirable from the standpoint of improving performance such as corrosion resistance.

The components of amorphous metals or alloys include iron, cobalt,
The main component is one or more transition metals such as nickel, and beryllium, magnesium, aluminum,
One or more components selected from the metal group such as titanium, vanadium, chromium, manganese, copper, zinc, zirconium, niobium, molybdenum, silver, indium, platinum, gold, and/or boron, carbon, silicon, A single element or multi-element obtained with or without the addition of one or more components selected from the group of non-metals and semi-metals such as phosphorus, germanium, antimony, etc., and their ancestry ratio. can be selected arbitrarily.

Moreover, any known method can be adopted as the manufacturing method. The main methods include spinning in rotating liquid, gun method,
Examples include the piston anvil method, atomization method, centrifugal quenching method, twin roll method, single roll method, etc., but all methods involve melting a molten metal or alloy at a cooling rate higher than the critical cooling rate at which the metal or alloy becomes amorphous. Any method that satisfies the conditions may be used. Moreover, there is no problem even if post-treatment such as heat treatment is performed after cooling.

The structure of the amorphous metal or alloy produced by the above-mentioned production method is so-called glass-like, and the arrangement of constituent atoms does not substantially have any long-period order. Therefore, the X″!IyA diffraction pattern is halo-like, showing a pattern clearly different from that of crystalline metals.

In the present invention, the amorphous wire is preferably 50% or more amorphous, but may have a partially crystalline structure.

As an example of the composition of the above amorphous wire, Fe
CoSiB, CoCrSiB, FeC
oCrSiB.

Fe? 5-ss BIs-fi Pets-as
Pro-rb Cm-+or Fe5q-atC
ra-q noh Btt-zz, Fe, @ al
e Si+z, Fehz MoteC+a r
Feaz CrI2Moa clll Fe
ab Cr1b MOzo CI8+C0tz
Si+s B+z + CO56Crzs C
1s, CO44FIOxb Cz.

COHCrze MOzo C+a, Nii4N11
4Crz4 C111 and the like. The above symbols are element symbols, and the subscript numbers represent the composition ratio or the range of the composition ratio.

Those without subscripts represent arbitrary composition ratios.

The amorphous wire of the present invention is not limited to these examples, and those having various composition ratios that meet the requirements of the present invention can be used. Furthermore, trace elements that are necessarily included in practical use are also optional.

Further, the wire electrode of the present invention has a wire diameter (diameter) of 8
It is necessary that the thickness is 0 μm or less, preferably 60 μm or less. For wire electrodes with wire diameters exceeding 8077 m, almost no improvement in electrostatic adhesion is observed.

Furthermore, the wire electrode of the present invention is characterized in that it does not exhibit a bead-like discharge phenomenon on the wire surface when a negative voltage is applied under tension to cause discharge.

The above-mentioned characteristics are essential requirements for not producing the aforementioned bound bubbles, and were first proposed by the present inventor. Since the bead-like discharge phenomenon is not observed with the positive voltage actually applied in the electrostatic cooling method, it is necessary to apply a negative voltage to cause the discharge to be observed.

The observation of the presence or absence of the bead-like discharge phenomenon is performed with tension applied to the wire electrode.

In the present invention, the negative voltage is about 6 kV or more, and the tension is about 600 g or more (that is, about 3° Okg per unit area (pongee 2)). The bead-shaped discharge phenomenon described above is performed in a dark room.

[aJ and [b] in Figure 1 use a wire with a wire diameter of 50 μm, apply a negative voltage of 6 kV under a tension tube of 300 kg/cm (588.8 g weight) to cause discharge, and check the discharge state. This is a schematic illustration of the results observed with the naked eye in a dark room.

The wire electrode of the present invention is as shown in FIG.
The corona (2) generated around the wire electrode (1) should have a parallel band shape and should not be a bead-shaped corona (2) as shown in FIG. 1 (bl).

Regarding the corona generated by the discharge phenomenon, the determination as to whether it is bead-shaped or not is that the depth of the concave groove of the corona (2) shown in Fig. 1(b) reaches the wire electrode, and as a result, no corona discharge occurs. Depends on whether or not to make it continuous.

According to the numerous observations made by the present inventors, most of the cases where grooves are present are deep enough to reach the wire electrodes, and it is relatively easy to determine whether the grooves are bead-shaped or not.

The bead-like discharge phenomenon is thought to be related to the surface condition of the amorphous metal or alloy, but the relationship between the two is not necessarily clear.

Therefore, the manufacturing method of the wire electrode having the above-mentioned characteristics of the present invention is not necessarily determined, but the material used (metal or alloy composition), the intended wire diameter, etc., and the cooling conditions for amorphization. It is necessary to obtain various wire electrodes by appropriately taking into account the above, and then conduct a discharge phenomenon test using the method described above to confirm the presence or absence of bead-like discharge, and then select an appropriate wire.

Further, the electrostatic applied cooling law wire electrode of the present invention preferably has a tensile breaking stress of 300 ky/am" or more. -layer preferably 330 kg102 or more, more preferably 360 kg/ll! or more. If the tensile breaking stress is less than 300 kg/ms, when thinner wire is used for the purpose of improving electrostatic adhesion, the wire cannot be stretched with sufficient tension, and the wire tends to vibrate, causing the film to deteriorate. This is undesirable because it may cause uneven thickness or cause spark discharge. Further, in the case of a winding type wire, the wire may break due to slight fluctuations in tension during the winding process, which is not preferable.

In addition, in the wire electrode of the present invention, the tensile strength at break determined from the wire diameter and tensile break stress is 10
It is preferable that the weight is 0g or more, more preferably 30g
The weight is 0 g or more, more preferably 600 g or more. If the tensile strength at break is less than 100 g weight, handling becomes extremely difficult and operations become extremely complicated.

Furthermore, the wire used in the present invention has a surface roughness (Ra
) is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably 0.01 μm or less. When the surface roughness (Ra) exceeds 0.1 μm, electric field concentration occurs due to unevenness on the surface of the wire, and spark discharge is likely to occur.

The electrostatic cooling method wire electrode of the present invention can be applied to the conventionally known electrostatic cooling method for thermoplastic resin sheets.

FIG. 2 is a schematic diagram of the electrostatic application cooling device according to the present invention. In Fig. 2, the molten thermoplastic resin sheet (1) extruded from the gouer is cooled and solidified by an electrically grounded metal rotary cooling body (2) and then taken out. At this time, a wire electrode (3) is provided near where the sheet first contacts the rotary cooling body, and a high voltage is applied. The wire electrode (3) is placed on the upper surface side of the sheet at a slight distance from the gou in a direction perpendicular to the flow direction of the sheet (1).

In FIG. 2, (2) represents a rotary cooling body, and (4) represents an end insulating support.

Examples of the molten thermoplastic resin to which the wire electrode of the present invention can be applied include polyesters, polyester ethers, polyamides, polycarbonates, polyester carbonates, polysulfones, polyethersulfones, polyetherimides, and polyolefins. ,
Examples include polymers such as ethylene, propylene, butene, and 4-methylpentene-1. Among the above-mentioned thermoplastic resins, the present invention is particularly effective in producing films of polyesters, such as polyethylene terephthalate, copolymers thereof, and polyethylene naphthalate. In addition, the wire electrode of the present invention is effective regardless of the electrical resistivity when the thermoplastic resin is melted, so
It is also effective against polysulfones and polyamides.

Although the present invention has been described in detail above, the present invention is not limited to the embodiment shown in FIG. 2 or the above-mentioned contents as long as it is desired to deviate from the gist thereof.

Therefore, for example, by using multiple wire electrodes and heating them,
Known techniques such as irradiating infrared rays to the contact area, attaching a cover to at least part of the top or side surface of the wire electrode, or using a roll with an insulating layer or a roll with a satin-like rough surface are used. May be combined.

〔Example〕

The present invention will be explained in more detail below with reference to Examples and Comparative Examples.

In the following Examples and Comparative Examples, wire electrodes were manufactured by the following rotating liquid spinning method, and the surface roughness (Ra) was measured by the following method.

<Manufacturing method of wire electrode> A 110 μm wire is drawn down in three stages using a diamond die to have a wire diameter of 50 to 60 μm. When pulling down, apply a known lubricant and apply a lubricant of 0.3 to lμ.
Use the filter beforehand. In addition, the final stage of unloading is performed in a clean room.

Under the above conditions, various wire electrodes were obtained by changing the purpose of the filter and the degree of cleanliness in the clean room.

<Measurement of surface roughness> The center line average roughness Ra (μm) is defined as the surface roughness. It was determined as follows using a surface roughness measuring instrument (SE-3FK) manufactured by Koita Research Institute.

That is, from a curved line measured in the longitudinal direction of the surface of the wire, a part of standard length L (2,51 rin) is extracted in the direction of its center line, and the center line of this extracted part is X-ray, and the direction of vertical magnification is Y-ray. When expressed as the axis by the roughness curve Y = f (x), the value given by the following formula is expressed in μm. However, the tip radius of the stylus was 2μ, the load was 30mg, and the cutoff value was 80μ.

Ra was measured at 10 points and the average value was calculated.

Example 1 After drying polyethylene terephthalate pellets with an intrinsic viscosity of 0.65, they were heated to 290°C in an extruder to melt them,
It was rapidly cooled using the cooling and solidifying device shown in FIG. 2, and the sort was molded.

As the rotating cooling body, an electrically grounded metal rotating roll with a length of 1600 mm and a mirror-finished surface was used.

The electrode is made of CO34CC034Crza+ a, and the discharge state is set to fi! under a tension of 1 kg and a negative voltage of 6 kV is applied. As a result,
As schematically shown in Figure 1(a), an amorphous wire (
(diameter: 60 μm), and was installed 5 steps away from the rotary cooling body.

While applying a DC voltage of 6 kV to the electrode, the extrusion amount and width were adjusted, and a sheet with a thickness of 150 μm was taken out.

Table 1 shows the operating conditions such as the maximum speed of the rotary cooling body, sheet thickness unevenness, number of spark discharges, number of wire cuts, etc., determined under conditions where no trapped air bubbles are present in the sheet.

Example 2 A wire with a thickness of 150 μm was prepared in the same manner as in Example 1, except that an amorphous wire with a diameter of 55 μm and the same composition was used, which was previously confirmed (ii) to exhibit no bead-like discharge phenomenon. A polyethylene terephthalate sheet was obtained. Table 1 shows the operating conditions.

Example 3 In Example 1, Fe6°CrhM with a diameter of 50μ was previously confirmed to not exhibit a bead-like discharge phenomenon.

A polyethyl terephthalate sheet having a thickness of 150 μm was obtained in the same manner as in Example 1, except that an amorphous wire made of B28 was used.

The operating conditions are shown in Table 1.

Comparative Example In Example 1, the electrode was an amorphous wire made of Co14Cr+5M0zoC+g with a diameter of 60 μm and a surface roughness of 0.01 μm. A polyethylene terephthalate sheet having a thickness of 150 μm was obtained in the same manner as in Example 1, except that the wire shown in 'b) in which many bead-shaped discharges were present was used. The operating conditions are shown in Table 1.

As shown in Table 1, when the wire electrode of the present invention, which does not cause bead-like discharge phenomenon, is used, the speed of the rotary cooling body increases under the condition that there are no bound bubbles in the sheet, causing uneven thickness, spark discharge, and wire electrodes. There was no problem with cutting, and productivity was good. On the other hand, when a wire electrode exhibiting a beads-like discharge phenomenon was used, the number of spark discharges was large, resulting in poor productivity.

Furthermore, in each Example and Comparative Example, the speed of the rotary cooling body was set to 60 m/min, and the state of adhesion of oligomers on the rotary cooling body was observed.

As a result, in each of the Examples, oligomers adhered to the surface of the rotary cooling body in the form of streaks, but the oligomers adhered little by little to the entire surface, and it was possible to operate for 6 days without cleaning.

In contrast, the comparative example required cleaning approximately every three days.

〔Effect of the invention〕

As detailed above, according to the electrostatic application cooling law wire of the present invention, in the electrostatic application cooling process of thermoplastic resin sheets, the electrostatic adhesion force is enhanced, the production speed is improved, and the spark discharge It is possible to achieve stable operation without wire breakage or wire cutting, and as a result, it is possible to dramatically improve the productivity of thermoplastic resin sheets and the films obtained by stretching them. This is of great significance.

[Brief explanation of the drawing]

FIG. 1 schematically shows the results of observing the tij and fog conditions of a wire electrode, where (a) shows the wire electrode of the example of the present invention, and (b) shows the wire electrode of the comparative ratio. show. FIG. 2 is a perspective view of an example of an electrostatic cooling device equipped with the electrodes of the present invention. The symbols in the figure are as follows. 1... Molten thermoplastic resin sheet 2... Rotating cooling body 3... Wire electrode 4... End insulating support Applicant Diafoil Co., Ltd. Agent

Claims (1)

[Claims] (1) A wire electrode used when applying an electrostatic charge to a molten thermoplastic resin extruded in a sheet form from a die using a wire electrode and bringing the resin sheet into close contact with a rotating cooling body, the wire electrode The wire must have a wire diameter of 80 μm or less, be made of an amorphous metal or alloy, and have the property of not exhibiting a bead-like discharge phenomenon on the wire surface when a negative voltage is applied and discharged under tension. An electrostatically applied cooling law wire electrode of a thermoplastic resin sheet.