JPH0873715A - Electrical insulating material - Google Patents

Abstract

PURPOSE: To obtain an electrical insulating material excellent in mechanical properties and electrical properties as well as handleability and workability. CONSTITUTION: There is provided an electrical insulating material made of a film having a thickness of 1 to 500μm and prepared by mixing a polyester having a melting point of 200 to 280 deg.C and an olefin/vinyl alcohol copolymer in a weight ratio of 70:30-98:2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric insulating material which is excellent in heat resistance, mechanical characteristics and electric characteristics, and is excellent in handleability and workability.

[0002]

2. Description of the Related Art Conventionally, as an electric insulating material in various fields, polyethylene terephthalate (hereinafter referred to as "
Films (sometimes referred to as PET) have been widely used. However, the conventional electrical insulating material made of a PET film has a drawback in that the strength of dielectric breakdown after heating at a constant temperature becomes small. For example, when an electrically insulating material made of a conventional PET film is used for an application that may be exposed to high temperatures such as an insulating material for gas insulated cables or a dielectric of a capacitor, dielectric breakdown may occur.

Further, in recent years, there has been a strong demand for miniaturization, weight reduction, and high performance of electric and electronic devices. For this purpose, the heat resistance of polyethylene terephthalate (class E, continuous allowable temperature of 120 ° C.) is not sufficient. Therefore, an insulating material having more excellent heat resistance is desired.

The polyethylene naphthalate film is an electrical insulating material suitable for this purpose (F type, continuous permissible temperature of 155 ° C.). For example, JP-B-53-35280, JP-B-54-1920, and JP-A-54-1920. 48-532
The characteristics are described in JP-A No. 99, JP-A-49-132600, JP-A-49-32200, and JP-A-50-133279.

As described above, it is widely known that a polyethylene naphthalate film (hereinafter sometimes referred to as PEN) basically has excellent heat resistance, mechanical properties and electrical properties. However, it has a low elongation and a large decrease in elongation after being subjected to a heat history for a long time, which makes it brittle.
In particular, in the case of insulating materials, as represented by, for example, motor insulation, it is molded in the shape of slots or wedges,
Insertion, coil winding, and coil formation are performed and used, but there is a problem that cracking easily occurs at that time and processing efficiency is poor, such as poor processing yield.

[0006]

An object of the present invention is to solve the above-mentioned problems of the prior art, and to fully develop the excellent heat resistance, mechanical properties, and electrical properties inherent in polymers. In addition, it is to provide an electrically insulating material having excellent handleability and workability.

[0007]

The object of the present invention is to obtain a melting point of 2
It can be achieved by a film having a thickness of 1 to 500 μm, which is obtained by mixing polyester of 00 to 280 ° C. and an olefin-vinyl alcohol copolymer in a weight ratio of 70:30 to 98: 2.

Preferably, the polymer constituting the above-mentioned film can be achieved mainly by polyethylene terephthalate or polyethylene naphthalate.

According to the present invention, the excellent heat resistance and mechanical properties originally possessed by the polymer are not provided until the above constitution is adopted.
Thus, it has become possible to provide an electrically insulating material having electrical characteristics and excellent handleability and workability.

In the present invention, by obtaining a film in which a polyester having a specific melting point is mixed with an appropriate amount of an olefin-vinyl alcohol copolymer, it is quite surprising that the polyester has excellent polymer properties that are inherently possessed. The inventors have found that in addition to obtaining heat resistance, mechanical characteristics, and electrical characteristics, they are extremely easy to handle and process, and the effect is much greater than in the prior art.

The polyester in the present invention is a polymer composed of a dicarboxylic acid component and a glycol component, and examples of the dicarboxylic acid component include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid and dicarboxylic acid. Aromatic dicarboxylic acids such as phenoxyethane dicarboxylic acid, 5-sodium sulfoisophthalic acid and phthalic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid and fumaric acid, cyclohexanedicarboxylic acid Examples thereof include alicyclic dicarboxylic acids such as acids and oxycarboxylic acids such as p-oxybenzoic acid.
Of these, terephthalic acid and naphthalenedicarboxylic acid are preferable from the viewpoint of heat resistance, mechanical properties, and electrical properties, and naphthalenedicarboxylic acid is particularly preferable for the purpose of heat resistance at higher temperatures.

On the other hand, as the glycol component, for example,
Aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, bisphenol A,
Examples thereof include aromatic glycols such as bisphenol S. Among them, ethylene glycol is preferable among these glycol components in terms of heat resistance, mechanical properties, and electrical properties. Cyclohexanedimethanol is also preferable because the strength of dielectric breakdown at high temperature does not decrease. Two or more kinds of these dicarboxylic acid components and glycol components may be used in combination.

Further, a copolymer of a polyfunctional compound such as trimellitic acid, trimesic acid and trimethylolpropane may be used as long as the effects of the present invention are not impaired.

The polyester used in the present invention is required to have a melting point of 200 to 280 ° C. from the viewpoint of heat resistance and the suppression of decomposition of the olefin-vinyl copolymer. The melting point is more preferably 23
The range of 0-280 degreeC and 250-280 degreeC is more preferable. Examples of such a preferable polymer include a homopolymer of polyethylene terephthalate or polyethylene naphthalate, or a copolymer. Here, it is preferable that the polyethylene terephthalate or polyethylene naphthalate unit, which is a structural unit, is contained in at least 70 mol% in all the polyester structural units in terms of heat resistance, mechanical properties and electrical properties. More preferably, it is desirable that the content is 80 mol% or more.

The polyester of the present invention preferably contains 0.01 to 1.5% by weight of a diethylene glycol component, more preferably 0.01 to 1.
The content is preferably 2% by weight, more preferably 0.01 to 1.0% by weight, because deterioration of the polyester due to heat history can be suppressed.

When the content of the diethylene glycol component is less than 0.01% by weight, the polymerization process becomes complicated, which is not preferable in terms of cost, and when it exceeds 1.5% by weight, the polyester is deteriorated due to a long thermal history. The heat resistance tends to decrease. Diethylene glycol is by-produced during the production of polyester, but in order to reduce the amount to 1.5% by weight or less, the polymerization time is shortened, and the amount of antimony compound, germanium compound, etc. used as a polymerization catalyst is limited. A method of combining phase polymerization and solid phase polymerization,
Examples of the method include adding an alkali metal component, but the method is not particularly limited.

The intrinsic viscosity [η] of the polyester is preferably in the range of 0.4 to 1.2, more preferably 0.
5 to 1.1 and 0.6 to 1.0 are more preferable and the mechanical properties can be improved.

In the present invention, olefin is added to polyester.
Vinyl alcohol copolymer in a weight ratio of 70:30 to 9
8: 2 contains excellent heat resistance, mechanical properties,
Moreover, in addition to the electrical characteristics, it is necessary in order to improve the handleability and workability. Furthermore, heat resistance, mechanical properties,
In terms of electrical properties, handleability, and processability, the olefin-vinyl alcohol copolymer is added to the polyester in a weight ratio of 80:
The content is preferably 20 to 97: 3, more preferably 90:10 to 95: 5. This means that the olefin-vinyl alcohol copolymer, which is difficult to be compatible with polyester, is dispersed in a sea-island shape, absorbs and disperses external force during handling and processing like a shock absorber, and has high impact resistance. It is thought that this is because it is obtained, and the effect is great. Although the reason is not clear, it has an effect of improving heat resistance and preventing the strength of dielectric breakdown after heating at a constant temperature from decreasing. The effect is particularly great in an atmosphere of high humidity.

Here, the olefin-vinyl alcohol copolymer is a copolymer generally obtained by saponifying a copolymer of an olefin and a vinyl ester such as vinyl acetate, and particularly has an olefin content of 10 to 60. Mol% is preferred, more preferably 20-50 mol% olefin-
Vinyl alcohol copolymers are suitable for greatly improving heat resistance, handleability, and processability. Further, those having a saponification degree of 90 mol% or more are preferable from the viewpoint of thermal stability.

The film of the present invention has a thickness of 1 to 500 μm.
In the range of m, it is preferably 10 to 300, more preferably 20 to 200 μm.

Further, the film of the present invention is preferably a biaxially oriented film in view of strength of dielectric breakdown and mechanical properties. The Young's modulus of such a film is preferably 400 kg / mm ² or more. More preferably 450 kg /
mm ² or more. The Young's modulus referred to here is an average value in the MD direction (longitudinal direction) and TD direction (width direction) of the film, and even if either one is extremely high, if it is outside this range as an average value, There is a tendency that the insertability of the film is insufficient, the handling property during film operation is reduced, it is difficult to handle, and the mechanical properties are unstable and inferior. This tendency becomes more remarkable as the film becomes thinner.

The film of the present invention has an average particle size of 0.1 to 10 μm in order to improve the handling and processability.
0.01 to 10% by weight of inorganic particles and / or organic particles are preferably contained, and further, 0.01 to 3% by weight of inorganic particles and / or organic particles having an average particle diameter of 0.1 to 5 μm. More preferably, it is contained. Examples of the inorganic particles and / or organic particles include wet silica, dry silica, colloidal silica, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay and the like and styrene, silicone, acrylic. Examples thereof include organic particles having an acid or the like as a constituent component. Of these, wet or dry silica or colloidal silica, inorganic particles such as alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene or the like are preferable. Two or more kinds of these particles may be used in combination.

Next, the method for producing the film of the present invention will be described, but the invention is not limited thereto. First, the polyester of the present invention can be produced by any conventionally known method and is not particularly limited. For example, the case of polyethylene naphthalate will be described. The dimethyl naphthalene-2,6-dicarboxylate and ethylene glycol were transesterified, and then germanium dioxide was added, followed by polycondensation reaction at a high temperature and a reduced pressure until a constant diethylene glycol content was obtained. obtain. In the production of such a polyester, a conventionally known reaction catalyst and a coloring inhibitor can be used, and examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt. Examples of the compound, the aluminum compound, the antimony compound, the titanium compound, and the anti-coloring agent include phosphorus compounds.
Then, the obtained polymer is subjected to solid-phase polymerization reaction at a temperature below its melting point under reduced pressure or under an inert gas atmosphere,
It is possible to obtain one having a predetermined intrinsic viscosity.

Thereafter, the polyester and the olefin-vinyl alcohol copolymer are supplied to a twin-screw vent type extruder, melted, discharged from an ordinary die, and then cooled and solidified by a cooling drum having a mirror surface or surface roughening. To obtain a cast film. At this time, it is preferable to employ a method of suppressing the heat generation by shearing in the extruder as much as possible, or a method of sealing with nitrogen gas so that the molten polymer does not come into contact with air.

The film of the present invention may be an unstretched sheet or a uniaxially stretched film, but it is preferably biaxially stretched from the viewpoints of mechanical properties, electrical properties, handleability and processability. It is a stretched film. In such a case, the unstretched sheet is biaxially stretched simultaneously or sequentially. In the case of sequential biaxial stretching, it is possible to perform stretching in the longitudinal direction or the width direction twice or more. The stretching ratio in the longitudinal direction and the width direction of the film can be arbitrarily set according to the orientation degree, strength and elastic modulus of the target film, but is preferably 2.5 to 5.0 times in each direction. is there. Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased, or they may be the same. The stretching temperature can be set to any temperature within the range of not less than the glass transition temperature of polyester and not more than the crystallization temperature, but it is usually preferably 80 to 150 ° C. After the biaxial stretching, the film is heat treated. This heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature above the crystallization temperature of the polyester and below the melting point, but it is preferably 150 to 250 ° C. The heat treatment time may be arbitrary, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in its longitudinal direction and / or width direction.

In producing the polyester film of the present invention, if necessary, additives such as an antioxidant, a plasticizer, an antistatic agent, a weatherproofing agent and a terminal blocking agent can be appropriately used.

The film of the present invention as it is is used as a tubing for electric and electronic devices, insulation in slots for phase insulation,
In addition to being widely used as an insulating material in a wide range of electric and electronic devices such as capacitor constituent materials, it may be used as a hybrid material for a secondary processed product by laminating with cloth, paper, glass or other inorganic insulating materials.

[0028]

[Measurement and Evaluation of Characteristics] The characteristics of the film were measured and evaluated by the following methods.

(1) Intrinsic viscosity of polyester Dissolve polyester in ortho-chlorophenol,
It was measured at 5 ° C.

(2) Melting Point of Polyester A polyester chip was crystallized and subjected to a differential scanning calorimeter (DSC-2 type manufactured by Perkin Elma Co.) at 10 ° C./m.
in. The heating rate was measured.

(3) Young's Modulus of Film It was measured according to ASTM-D-882-81 (method A) (pulling speed: 300 mm / min). The value was obtained as an average value in the MD direction (longitudinal direction) and the TD direction (width direction) of the film.

(4) Suitability for processing A film was cut out so that the film was 40 mm in the longitudinal direction and 20 mm in the width direction, and then both ends were folded back by 5 mm in parallel to the width direction to prepare a sample for inserting a motor. This sample was inserted into the motor rotor portion, and the enamel wire was wound therein. After that, the enamel portion was pressed to form the enamel wire portion, and at this time, the generation state of cracks in the film sample was evaluated.

(5) Dielectric Breakdown Strength According to JIS C2318-1966, it was measured by an AC short time boosting method.

[0034]

【Example】

Example 1 First, as a polyester, PET (melting point 255 ° C., intrinsic viscosity [η] 0.65) in which an acid component is terephthalic acid and a glycol component is ethylene glycol is added to an olefin-
A vinyl alcohol copolymer (ethylene content 46 mol%) was blended at a weight ratio of 90:10, supplied to a twin-screw vent type extruder, melted, discharged from an ordinary die and cooled and solidified by a cooling drum. Then, a cast film was obtained.

Then, a longitudinal biaxial stretching method 3.5 is used.
The film was stretched twice and laterally 3.7 times and heat-treated to obtain a biaxially oriented film having a thickness of 20 μm. Young's modulus of the film is 440
It was kg / mm ² .

The film thus obtained was evaluated for processing suitability and found to have no cracks and had good processability.

When the obtained film was heated at 160 ° C. for 1 hour, the strength of dielectric breakdown was evaluated.
It was 8 kV, and it was not so much lower than the dielectric breakdown strength of 11.0 kV before heating.

Example 2 Polyethylene 2,6 naphthalate (melting point 265 ° C., intrinsic viscosity [η] 0.6) was used as polyester, and olefin-vinyl alcohol copolymer (ethylene content 4
(6 mol%) at a weight ratio of 95: 5, and the mixture is quantitatively supplied to a biaxially vented extruder and sequentially biaxially stretched to give a thickness of 20.
A biaxially oriented film of μm was obtained. The Young's modulus of the film was 650 kg / mm ² .

When the film was evaluated for processability using this film, no cracking occurred at all and it had good processability.

Further, when the obtained film was heated at 160 ° C. for 1 hour, the strength of dielectric breakdown was evaluated.
It was 4 kV, which was not so much lower than the dielectric breakdown strength of 11.5 kV before heating.

Comparative Example 1 Polyethylene 2,6 naphthalate (melting point 265 ° C., intrinsic viscosity [η] 0.7) was used alone as the polyester, extruded in the same manner as in Example 2 and sequentially biaxially stretched to obtain a thickness. A 30 μm biaxially oriented film was obtained. The Young's modulus of the film was 700 kg / mm ² . As a result of processing suitability evaluation using this film, cracks occurred,
It was inferior in workability.

Comparative Example 2 As polyesters, polyethylene 2,6 naphthalate (melting point 265 ° C., intrinsic viscosity [η] 0.7) and polyethylene terephthalate (melting point 255 ° C., intrinsic viscosity [η] =
0.65) was blended in a weight ratio of 80:20, extruded in the same manner as in Example 2 and sequentially biaxially stretched to obtain a biaxially oriented film having a thickness of 20 μm. The Young's modulus of the film was 670 kg / mm ² . As a result of processing suitability evaluation using this film, although less frequent than that of Comparative Example 1, the occurrence of cracks was recognized and the workability was poor. Moreover, the strength of the dielectric breakdown after the obtained film was heated at 160 ° C. for 1 hour was evaluated.
It was 2 kV, and it was recognized that the breakdown strength was 11.3 kV, which was clearly lower than that before heating.

[0043]

EFFECTS OF THE INVENTION The polyester film for electrical insulation of the present invention is excellent in handleability and processability in addition to mechanical properties and electrical properties, so that the process yield can be improved in insulating applications such as motor insulation. Furthermore, it has a feature that it is also good in terms of reliability.

The insulating film of the present invention can be suitably used for motor insulating applications where there is a strong demand for downsizing, weight reduction and high performance, and also for electrical insulating applications other than motor insulating applications.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C08L 29:04)

Claims (4)

[Claims] 1. A weight ratio of a polyester having a melting point of 200 to 280 ° C. and an olefin-vinyl alcohol copolymer is 7
It is mixed at 0:30 to 98: 2 and has a thickness of 1 to 500.
An electrically insulating material comprising a film of μm. 2. The electrical insulating material according to claim 1, wherein the polyester is mainly composed of polyethylene terephthalate or polyethylene naphthalate. 3. A polyester mainly having a melting point of 250 to 2
It consists of polyethylene terephthalate or polyethylene naphthalate of 80 degreeC, The electrical insulating material of Claim 1 or Claim 2 characterized by the above-mentioned. 4. The Young's modulus of the film is 400 kg / mm.
^{It is 2} or more, The electrical insulating material in any one of Claim 1- Claim 3 characterized by the above-mentioned.