JPH06335960A - Processing of electrical insulating polyethylene naphthalate film - Google Patents

Abstract

PURPOSE:To obtain an improved technology processing a polyethylene naphthalate (PEN) film to produce a slot or wedge being an electrical insulating material. CONSTITUTION:When a biaxially oriented PEN film with a thickness of-125-450mum is processed into a slot or wedge being the electrical insulating material in a motor, a processing method holding the temp. of the film to 25-80 deg.C to prevent delamination during processing and a molding processing method setting the radius of curvature of the leading end of a processing punch at the time of the molding processing of the wedge to 75-500mum and adjusting the clearance between the wall surface of the punch and a die to [film thickness + (75-400mum)] are employed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved method for processing biaxially oriented polyethylene-2,6-naphthalate film into slots or wedges as an electrically insulating material in motors.

[0002]

2. Description of the Related Art A polyethylene terephthalate (hereinafter PET) film is used because it has heat resistance to some extent as an electric insulating material for a general motor, suitability for automatic molding, and economical efficiency. Has been used.

In the form of the insulating material, for example, in a slot, both ends are bent and then shaped into a U-shape as shown in FIG. 1 and inserted into the groove of the stator. Further, the wedge is formed into a U shape as schematically shown in FIG. 2 and inserted between the coils or inside the coil.

With the recent miniaturization and higher performance of electric and electronic devices, there have been increasing demands for high levels of heat resistance of insulating materials for these motors.

However, since the PET film cannot withstand high temperature and long-term use, aramid paper or polyimide film is used as an insulating material. However, all of these materials are very expensive, and there is a problem in economic efficiency.In particular, in the case of aramid paper, since it is not rigid, it is bent when inserting slots and wedges and automatic insertion cannot be done. is there.

On the other hand, in the case of a motor of a hermetic compressor used in a refrigerator or an air conditioner, the insulating material is used in the harsh environment of high temperature and high pressure in the coexistence of refrigerant and lubricating oil. At this time, if a large amount of the oligomer contained in the film is eluted in the refrigerant or the lubricating oil, the oligomer may become a serious obstacle such as clogging of the nozzle or sticking to the inside of the cylinder to cause a locking phenomenon. Further, it is a new alternative refrigerant related to the complete abolition of specified CFCs, and the refrigerant and the corresponding lubricating oil have a property of easily absorbing moisture. When a conventional ordinary PET film is used as an insulating material, it is feared that the durability will be long-term due to hydrolysis. ing.

As described in detail above, there is a demand for an insulating material which has heat resistance, a low oligomer elution property, an excellent hydrolyzability and a certain economical efficiency as compared with the current PET film. Various polymer films have been proposed as those capable of withstanding these requirements, and among them, biaxially oriented polyethylene-2,6-naphthalate film has been attracting attention as a particularly excellent one. However, although this film has excellent performance, it is harder and more rigid than PET. And if you use the conventional processing machine as it is, you can mold into slots or wedges,
When it is inserted, it is subject to shocking deformation, which may cause cracking or delamination, which may cause insulation failure.
There is a problem that the machine stops due to clogging in the automatic molding machine. In other words, it is difficult to perform stable continuous processing.

[0008]

As described above, the thickness 125
It was extremely difficult to stably process a biaxially oriented polyethylene-2,6-naphthalate film having a thickness of ˜450 μm into a slot or wedge for electrical insulation.

An object of the present invention is to provide an improved processing method for a biaxially oriented polyethylene-2,6-naphthalate film which solves the above problems.

[0010]

The present inventors have completed the present invention as a result of repeated studies to achieve the above object.

That is, the first aspect of the present invention is that the thickness is 125 μm.
When a biaxially oriented polyethylene-2,6-naphthalate film of m to 450 μm is formed into a slot or wedge which is an electrically insulating material in a motor, the film temperature during processing is set to 25 ° C to 80 ° C. Is a method for processing a polyethylene-2,6-naphthalate film for electrical insulation.

The second aspect of the present invention is to form a biaxially oriented polyethylene-2,6-naphthalate film having a thickness of 125 μm to 450 μm into a wedge which is an electrically insulating material in a motor. Polyethylene-2,6-naphthalate for electrical insulation, characterized in that the radius of curvature R is set to 75 μm to 500 μm and the clearance on one side obtained by subtracting the film thickness from the gap between the punch wall surface and the die is set to 75 μm to 400 μm This is a film processing method.

The polyethylene-2,6-naphthalate in the present invention is not only a polyethylene-2,6-naphthalate homopolymer but also a small proportion (for example, 10 mol% or less, further 5 mol% or less) of the third component. It also includes a modified polyethylene-2,6-naphthalate copolymer and a blend polymer in which a small proportion (for example, 20% by weight or less, further 10% by weight or less) of a third component is mixed.

This polyethylene-2,6-naphthalate is basically known and can be produced by a known method. For example, polyethylene-2,6-naphthalate is generally produced by subjecting 2,6-naphthalenedicarboxylic acid or its ester-forming derivative and ethylene glycol or its ester-forming derivative to polycondensation reaction in the presence of a catalyst. It In the case of producing a copolymer, the third component may be added and reacted until the condensation polymerization reaction is completed, and in the case of producing a blended polymer, the polymer of the third component may be added before the film formation. Should be mixed.

Suitable third component is a compound having a divalent ester-forming functional group, for example, oxalic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, 2,7.
-Dicarboxylic acids such as naphthalenedicarboxylic acid and diphenyl ether dicarboxylic acid or lower alkyl esters thereof; oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid or lower alkyl esters thereof; or propylene glycol, trimethylene glycol And dihydric alcohols such as tetramethylene glycol, hexamethylene glycol, neopentyl glycol and the like.

Further, polyethylene-2,6-naphthalate may be obtained by blocking some or all of the terminal hydroxyl groups and / or carboxyl groups with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. Alternatively, it may be modified with a trifunctional or higher functional ester-forming compound such as glycerin or pentaerythritol in an extremely small amount within a range where a substantially linear polymer is obtained.

The polyethylene-2,6-naphthalate may contain a lubricant such as finely divided silica, talc, clay or the like for imparting a slip property to the film, and other additives such as a stabilizer and an ultraviolet ray. Absorbents, colorants, flame retardants and the like can also be added.

Here, a wedge forming step will be described in detail as an example of the forming process. FIG. 3 shows a cross section of the wedge molding machine. Although it depends on the model and capacity of the motor, it is cut into a width of 10 to 15 mm and a length of 50 to 80 mm in a motor for a compact hermetic compressor such as a refrigerator. The film 1 is inserted into the portion shown by the dashed line in the upper part of FIG. After that, the die 2 is pushed by the punch 2 from above.
It is pushed downward along with and inserted into the magazine 4. In this step, the film undergoes compositional deformation and is processed into the U shape shown in FIG. The film processed here is subjected to shearing forces in a very short time due to bending stress and movement of the punch, and due to friction with the die. As a result, delamination is likely to occur at the bent portion or the cut end portion. This delamination hardly occurs in a normal PET film, but occurs frequently in a biaxially oriented polyethylene-2,6-naphthalate film. Since the polyethylene-2,6-naphthalate film is more easily oriented in the direction of the upper surface of its molecular structure than the PET film, it is peeled into layers when impacted by bending stress and shearing force.

By the way, as shown in the present invention (first invention), when the temperature of the biaxially oriented polyethylene-2,6-naphthalate film during processing is 25 ° C. or higher, the phenomenon of delamination tends to be greatly reduced. is there. It is considered that this phenomenon is such that the film is softened and plasticity is increased by increasing the film temperature at the time of processing, so that the film is not peeled off even when an impact stress is applied. This temperature needs to be 25 ° C. or higher, more preferably 30 ° C. or higher. Although a higher temperature is preferable from the viewpoint of delamination, if the temperature is too high, the film softens and the processing machine stops when caught between the punch and the die during processing, or the truncated pyramidal shape becomes a distortion. Therefore, the temperature should be 80 ° C or lower. Of course, 70 ° C or lower is desirable.

Biaxially oriented polyethylene-2,6-of the present invention
A known method can be used for the biaxial stretching in the production of naphthalate, and the biaxial stretching may be either sequential biaxial stretching in the machine direction and transverse direction, or similar biaxial stretching.

The heating method is not particularly limited as the film temperature in the processed portion may be substantially 30 ° C. to 80 ° C. For example, hot air is blown to the processed portion while controlling the temperature. Alternatively, a method of controlling the film temperature by embedding a heater of a machine part in the processed portion and thereby generating heat can be applied.

Next, the present invention (second invention) will be explained. Normally, the punch is designed so that the radius of curvature R of the punch is 30 to 50 μm and the clearance is 30 to 50 μm. The reason for this is that with a soft material such as PET film, as described above, a truncated pyramidal shape is not formed unless R and clearance are of this extent, so that mounting in the magazine 4 shown in FIG. Because it will be defective.

When a biaxially oriented polyethylene-2,6-naphthalate film is bent and formed by a punch, a strong stress is locally applied to the bent portion, so that delamination tends to occur. The reduction of the absolute value of this stress and the relaxation of the degree of the working pole are effective for preventing delamination.

The radius of curvature R of the punch is 75 μm or more, preferably 100 μm or more, and the clearance is 75 μm or more,
Preferably, the thickness is 100 μm or more so that the above-mentioned layer peeling hardly occurs.

However, if the punch R is too large or if the clearance is too large, the film will be caught between the punch and the die during wedge forming, causing the trouble of stopping the processing machine, or cutting the head of the pyramid. The shape of the wedge is insufficient (the mouth widens), and the above-mentioned wedges may not be properly attached to the magazine or the motor. Therefore, the punch R is preferably 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less, and the clearance is preferably 400 μm or less, preferably 300 μm or less, more preferably 250 μm or less. Of course, the punch R and the clearance can be appropriately set depending on the thickness of the processed film, the physical properties thereof, the size of the wedge, the processing speed, etc. within the above range.

Biaxially oriented polyethylene-2,6-of the present invention
A known method can be used for biaxial stretching in producing naphthalate, and either sequential biaxial stretching in the machine direction and transverse direction or simultaneous biaxial stretching can be selected.

[0027]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

Molding of wedges in Examples and Comparative Examples is carried out as follows. Using a wedge molding part of a motor processing machine manufactured by Odawara Engineering Co., Ltd., using a film having a thickness of 250 μm and a width of 12 μm, a length of 6
Form a 0 mm wedge as shown in FIG.

The presence or absence of layer peeling is visually determined for the 20 wedges thus obtained, and the occurrence ratio is shown as a percentage.

The processing stability during processing is judged as follows. 100 wedges No scratches during molding are regarded as good, and if the processing machine is stopped even once even once, it is regarded as defective.

Further, in order to evaluate the U-shaped form, the width of the wedge (indicated by W in FIG. 2) is measured with a micrometer.

Next, the curvature R of the punch tip is measured as follows. Toyo Kagaku Kenkyu Silicon Patty (product Patek) is applied to the tip of the punch, and after curing, it is peeled and sliced, and a cross-section of the photograph is magnified 50 to 100 times to measure the radius of curvature R. .

The clearance is measured as follows.
The thickness of the punch and the gap between the dies are measured with a micrometer to obtain a value obtained by subtracting the thickness of the film from 1/2 of the difference between the two.

The processing speed of the wedge is 2 pieces / second, and the processing test is performed at room temperature (20 ° C.) and relative humidity of 65%.

[0035]

Examples 1 to 4 and Comparative Examples 1 to 4 Polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.60 was melt extruded from a die slit by a conventional method, and cooled and solidified on a casting drum to prepare an unstretched film. This was biaxially stretched at a longitudinal stretching ratio of 3.0 and a lateral stretching ratio of 3.3, and then heat-fixed at 230 ° C. and cooled under tension to obtain a film having a thickness of 250 μm. This film was wedged by the method described above. Here, the processing machine and the film were brought into a large-sized constant temperature and humidity chamber for processing and evaluation.

The temperature inside the thermo-hygrostat is the temperature shown in Table 1 ± 1 ° C
Controlled by. The relative humidity was controlled at 60 ± 5%. The wedge processing was carried out after about 3 hours had elapsed from the start of temperature control in order to make the temperature of the wedge processing machine and the film temperature coincide with the set temperature.

The results obtained are shown in Table 1.

[0038]

[Table 1]

As is clear from the above results, in the method for processing the biaxially oriented polyethylene-2,6-naphthalate film of the first invention, there is almost no delamination of wedges, and there are problems such as catching during processing. I couldn't see it at all.

On the other hand, in Comparative Examples 1 and 2 having a low film temperature, Comparative Examples 3 and 4 having a high frequency of layer peeling and having a high film temperature did not cause layer delamination, but there was a catch during processing. There was a problem of stopping the processing machine.

[0041]

Examples 5 to 8 The film obtained in Example 1 was used for wedge processing.

Punch Tip R and Clearance The levels listed in Table 2 were implemented.

[0043]

Comparative Example 5 Polyethylene terephthalate having an intrinsic viscosity of 0.65 was formed into a film having a thickness of 250 μm in the same manner as in Example 5, and the above-mentioned wedge processing was performed. Punch R and the ones listed in Table 2 were used.

[0044]

Comparative Examples 6 to 10 The films of Examples 5 to 8 were used, and the punch R and the clearances shown in Table 2 were used.

The results obtained are shown in Table 2. The materials of the films in the table are as follows. PEN: biaxially oriented polyethylene-2,6-naphthalate; PET: biaxially oriented polyethylene terephthalate,

[0046]

[Table 2]

As is clear from the above results, in the method for processing the biaxially oriented polyethylene-2,6-naphthalate film of the second invention, there is almost no delamination of wedges, and there are also problems such as catching during processing. I couldn't see it at all. In addition, the W dimension, which shows the shape retention of the wedge, is the same as the existing P dimension.
The shape of the truncated pyramid was equal to or less than ET, and was firm.

On the other hand, the punch R or Comparative Examples 6 to 8 having a small clearance has a W dimension smaller than that of PET and a good morphology, but the frequency of delamination is extremely high. Further, in Punch R or Comparative Examples 9 to 10 having a large clearance, there was no delamination, but the processing stability was poor, and since the W dimension was large and the spread of the wedge was large, only the morphology was poor.

[0049]

EFFECT OF THE INVENTION Polyethylene-2 for electrical insulation of the present invention
The processing method of the 6-naphthalate film is excellent in quality such as no delamination and excellent in processing stability.

[Brief description of drawings]

FIG. 1 is a perspective view of a film of the present invention formed into a slot.

FIG. 2 is a perspective view showing a state where the film of the present invention is formed into a wedge. In the drawing, W indicates the apparent width when the bending process is performed.

FIG. 3 shows a cross-sectional view of a wedge molding machine. In the drawings, 1 is a film of the present invention, 2 is a punch, 3 is a die and 4 is a magazine.

Claims (2)

[Claims] 1. When forming a biaxially oriented polyethylene-2,6-naphthalate film having a thickness of 125 μm to 450 μm into a slot or wedge which is an electrically insulating material in a motor, the film temperature at the time of processing is 25 ° C. to 80 ° C. A method for processing a polyethylene-2,6-naphthalate film for electrical insulation, which is characterized in that the temperature is ℃. 2. When forming a biaxially oriented polyethylene-2,6-naphthalate film having a thickness of 125 μm to 450 μm into a wedge which is an electrically insulating material in a motor, the R (curvature radius) of the punch of the processing machine is 75 μm. To 500 μm and the clearance on one side, which is obtained by subtracting the film thickness from the gap between the punch wall surface and the die, is 75 μm.
A method of processing a polyethylene-2,6-naphthalate film for electrical insulation, characterized in that the thickness is from 400 to 400 μm.