JP2002245857A - Biaxially oriented film for electric insulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented film for electric insulation made of low oligomer with excellent processing property and long-term heat resistant property. SOLUTION: The biaxially oriented film for electric insulation is composed of a resin component made of polyester as a main component, and contains polyimide, and the content of cyclic trimer is not less than 0.1 weight % and not more than 0.5 weight %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for electrical insulation, and more particularly, to a polyester film for electrical insulation.
The present invention relates to a polyester film for electrical insulation which is excellent in properties (for example, low oligomer properties, processing properties, and long-term heat resistance) required for motor insulation applications such as refrigerators and various electrical insulation applications.

[0002]

2. Description of the Related Art Conventionally, biaxially stretched polyethylene terephthalate films have been widely used as electrical insulating materials because of their excellent heat resistance, mechanical properties, electrical properties, and workability. However, in recent years, miniaturization, weight reduction, and high performance of electric and electronic devices have been desired. For this purpose, polyethylene terephthalate has heat resistance (E class,
Since the continuous use allowable temperature (120 ° C.) is insufficient, an insulating material having better heat resistance is desired. Particularly in refrigerator motors used in coolers, refrigerators, freezers, and the like, the operating temperature rises along with the miniaturization, and the continuous use temperature is improving. Therefore, the market demand for improving the heat resistance of the film is particularly strong. Further, as the operating temperature rises and the refrigerant changes, there is an increasing demand for reducing components (for example, oligomers in the film) extracted by the refrigerant.

[0003] As insulating materials suitable for the purpose of increasing the continuous use temperature, for example, Japanese Patent Publication No. 53-35280, Japanese Patent Publication No. 54-1920, Japanese Patent Application Laid-Open No. 48-43198, and Japanese Patent Application Laid-Open No. 62-115609. In gazettes and the like, a biaxially stretched polyethylene naphthalate film having a performance of an allowable continuous use temperature of 155 ° C. has been proposed. However, while polyethylene naphthalate film has excellent heat resistance, mechanical properties, and electrical properties, when applied to motor insulation, etc., it is molded into slots or wedges and inserted into the motor or coil-molded. However, there is a problem that cracks are likely to occur at that time and the processing yield is reduced. Therefore, improvement of the processing characteristics has been desired.

[0004] Further, regarding the blend of polyester and polyetherimide (PEI) related to the present invention,
It is known that the glass transition temperature increases with an increase in the PEI fraction (for example, US Pat. No. 4,141,927).
No., “JOURNAL of APPLIED POLY
MER SCIENCE 48 935-937 (19
93) ", Macromolecules 282
845-2851 (1995), POLYMER, 38
4043-4048 (1997) "). However, there are few reports on a biaxially oriented film composed of a blend of polyester and PEI, and there is no technical knowledge at all about using the resin composition for a biaxially oriented film for electrical insulation. .

[0005]

SUMMARY OF THE INVENTION The present invention overcomes the problems of the prior art and provides a biaxially oriented film for electrical insulation, which is a low oligomer and has excellent processing characteristics and long-term heat resistance. It is the purpose.

[0006]

Means for Solving the Problems The present invention has the following arrangement to achieve the above object. That is, the present invention is directed to a film comprising a resin composition containing a polyester as a main component and a polyimide, wherein the oligomer content is 0.1% by weight or more and 0.5% by weight or less. The main point is the film.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the biaxially oriented film for electrical insulation of the present invention will be described below.

The polyester as used in the present invention is a polymer containing at least 80% by weight of a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid. Dicarboxylic acids are represented by terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like, and diols are ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane It is represented by dimethanol and the like. Specific examples of polyester include, for example, polymethylene terephthalate, polyethylene terephthalate, polypropylene terephthalate, polyethylene isophthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-
Examples thereof include 1,4-cyclohexane dimethylene terephthalate and polyethylene-2,6-naphthalate. Of course, these polyesters may be homopolymers or copolymers.
As copolymerization components, for example, diol components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, adipic acid, sebacic acid, phthalic acid,
It may contain a dicarboxylic acid component such as isophthalic acid and 2,6-naphthalenedicarboxylic acid, and a hydroxycarboxylic acid component such as hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

In the present invention, polyethylene terephthalate, polyethylene-2,6-naphthalate, a copolymer or a modified product thereof are preferred, and a polymer containing at least 70 mol% of an ethylene terephthalate unit is particularly preferred. Particularly preferred from the viewpoint. In this case, the acid component is mainly terephthalic acid, but a small amount of another dicarboxylic acid component may be added as a copolymer component,
The glycol component is mainly composed of ethylene glycol, but another glycol component may be added as a copolymer component.

Examples of dicarboxylic acids other than terephthalic acid include naphthalenedicarboxylic acid, isophthalic acid, diphenylsulfonedicarboxylic acid, benzophenonedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 3,3
Aromatic dicarboxylic acids such as' -diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, succinic acid, azelaic acid, sebacic acid, and dodecandioic acid; fats such as hexahydroterephthalic acid and 1,3-adamantanedicarboxylic acid And cyclic dicarboxylic acids.
Examples of glycol components other than ethylene glycol include, for example, chlorohydroquinone, methylhydroquinone, 4,4′-dihydroxybiphenyl, 4,4′-
Aromatic diols such as dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfide, 4,4'-dihydroxybenzophenone, p-xylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexane Diols, neopentyl glycol, 1,4-cyclohexanedimethanol, etc.
1,4-butanediol, 1,6-hexanediol,
Aliphatic and alicyclic diols such as neopentyl glycol can be mentioned. Further, in addition to the acid component and the glycol component, p-hydroxybenzoic acid, m-hydroxybenzoic acid, aromatic hydroxycarboxylic acids such as 2,6-hydroxynaphthoic acid and p-aminophenol,
If p-aminobenzoic acid or the like is used in such a small amount as not to impair the object of the present invention, it can be further copolymerized.

The intrinsic viscosity of the raw material of the polyester used in the present invention is preferably 0.70 from the viewpoints of melt kneading with polyimide, film forming property, polymer decomposition during melt extrusion and the like.
-1.5 dl / g, more preferably 0.8-1.2 dl
/ G.

The polyester raw material used in the present invention has a ratio of a metal compound to a phosphorus compound (M / P) of 0.7.
As described above, the ratio is preferably 1.2 or less in order to suppress the regeneration of the oligomer during the film forming process and obtain the film disclosed in the present invention. Here, M is the number of moles of the metal compound converted from the amount of the metal element contained in the polyester (ppm), and P is the number of moles of the phosphorus compound converted from the amount of the phosphorus element contained in the polyester (ppm). It is.
The more preferable M / P of the polyester raw material is 0.75 or more and 1.1 or less.

Hereinafter, specific examples of obtaining a polyester raw material will be described, but it is a matter of course that the present invention is not restricted by these descriptions.

The dicarboxylic acid or its ester derivative and a glycol component such as ethylene glycol are heated and dissolved in the presence of an esterification or transesterification catalyst and esterified or transesterified by a conventional method. After completion of the esterification or transesterification reaction, M
A metal compound and / or a phosphorus compound are added so that / P falls within the preferred range described above, and then the temperature is increased by a conventional method.
A polycondensation reaction is performed under reduced pressure to obtain a polyester having an intrinsic viscosity of about 0.5 dl / g. The obtained polyester is subjected to solid-state polymerization by heating under a reduced pressure, a normal pressure, or a nitrogen atmosphere under a suitable condition. The conditions of the solid-state polymerization temperature and the solid-state polymerization time can be appropriately changed depending on the type and amount of the metal compound added to the polyester, the type and amount of the phosphorus compound, the intrinsic viscosity and the like. In the present invention, after preliminarily crystallizing at a temperature of 180 ° C. or less, 1 to 190 ° C. to 250 ° C.
It is preferred to carry out solid phase polymerization under reduced pressure of about rr for 10 to 35 hours. Further, as a polymerization catalyst in the polycondensation reaction,
An ordinary polyester polymerization catalyst can be used as appropriate. For example, antimony compounds such as antimony trioxide, 2
Examples thereof include manganese-based compounds such as manganese oxide, germanium-based compounds such as germanium oxide, various titanium-based compounds, and aluminum-based compounds.

The polyimide in the present invention is a melt-moldable polymer containing a cyclic imide group, and is not particularly limited as long as it can meet the purpose of the present invention, but may be aliphatic, alicyclic or aromatic. A polyetherimide containing a system ether unit and a cyclic imide group as a repeating unit is preferred. For example, U.S. Patent Nos. 4,141,927, 2,622,678 and 2,606,912.
No. 2,606,914, Patent 2,596,565
And polyetherimides described in Japanese Patent Nos. 2596566 and 2598478;
No. 36, Japanese Patent No. 2599171, JP-A-9-4
8852, Japanese Patent No. 2565556, Japanese Patent No. 256
No. 4636, Patent No. 25664637, Patent No. 2563
No. 548, Japanese Patent No. 2563547, Japanese Patent No. 25583
No. 41, Patent No. 2558339, Patent No. 283458
Polymers described in Japanese Patent Publication No. 0, each publication.

In addition, as long as the effects of the present invention are not impaired, structural units other than cyclic imide and ether units, for example, aromatic, aliphatic, alicyclic ester units, oxycarbonyl units, etc. May be contained.

In addition, as long as the effects of the present invention are not impaired, structural units other than cyclic imide and ether units, such as aromatic, aliphatic and alicyclic ester units, oxycarbonyl Units and the like may be contained.

As specific examples of the polyetherimide that can be preferably used in the present invention, a polymer represented by the following general formula can be exemplified.

[0019]

Embedded image (Wherein, R ₁ is a divalent aromatic or aliphatic residue having 6 to 30 carbon atoms, and R ₂ is
A divalent aromatic residue having 6 to 30 carbon atoms,
Selected from the group consisting of alkylene groups having 20 carbon atoms, cycloalkylene groups having 2-20 carbon atoms, and polydiorganosiloxane groups chain terminated with alkylene groups having 2-8 carbon atoms. And a divalent organic group. Examples of the above R ₁ and R ₂ include aromatic residues represented by the following formula group.

Embedded image

In the present invention, polyetherimide having a glass transition temperature of preferably 350 ° C. or lower, more preferably 250 ° C. or lower is preferable from the viewpoints of compatibility with polyester, cost, and melt moldability. Condensates of 2,2-bis [4- (2,3-dicarboxyphenoxy) phenyl] propane dianhydride with m-phenylenediamine or p-phenylenediamine having structural units, copolymers thereof and modifications thereof The body is most preferred from the viewpoint of compatibility with the polyester, cost, melt moldability and the like. This polyetherimide is manufactured by GE Plastics, Inc. and is referred to as "Ultem 1000, 5000,
And 6000 series ".

[0021]

Embedded image Or

Embedded image

In the film of the present invention, it is essential that the content of the cyclic trimer is 0.1% by weight or more and 0.5% by weight or less. Here, the cyclic trimer is a cyclic trimer contained as an oligomer component of the polyester constituting the film, and its content can be measured by liquid chromatography. When the content of the cyclic trimer exceeds 0.5% by weight, when the refrigerator motor or the like is used in a state immersed in the refrigerant, there is a problem that a substance extracted from the film by the refrigerant precipitates. It is not suitable for electrical insulation because it easily occurs. On the other hand, the content of the cyclic trimer was 0.1% by weight.
Since it is extremely difficult industrially to make it less than 0.1% by weight or more in practical use. When used for electrical insulation, the amount of the cyclic trimer extracted from the film by the refrigerant increases as the operating temperature increases, and therefore, in applications used at high temperatures, the problem involving the cyclic trimer is particularly important. Is big. Therefore, the content of the cyclic trimer in the film of the present invention is preferably from 0.1% by weight to 0.4% by weight, particularly preferably from 0.1% by weight to 0.3% by weight.

The polyimide content in the film of the present invention is preferably from 5% by weight to 35% by weight, and from the viewpoint of processing characteristics and long-term heat resistance, is from 7% by weight to 20% by weight. Is more preferable. When the content of the polyimide is less than 5% by weight, it is difficult to obtain the effect desired in the present invention, and conversely, 35% by weight.
Exceeding the limit may cause problems in film forming properties, cost, processing characteristics, and the like.

The intrinsic viscosity of the film is not particularly limited, but is preferably in the range of 0.65 to 1.2 dl / g. Intrinsic viscosity is 0.7 to 0.7 from the viewpoint of achieving the productivity of the film and the heat resistance and processing characteristics aimed at in the present invention.
0.9 dl / g is more preferred.

Various additives may be added to the resin used in the present invention, if necessary. Various inorganic and organic lubricants can be used as additives. As the shape, various shapes such as agglomerated particles, true spherical particles, beads, particles, and scale-like particles can be used. In the case of inorganic particles, examples of the material include silicon oxide, calcium carbonate, titanium oxide, alumina, zirconia, aluminum silicate, mica, clay, and talc. In the case of the organic particles, examples of the material include a polyimide resin, an olefin or a modified olefin resin, a crosslinked or non-crosslinked polystyrene resin, a crosslinked or noncrosslinked acrylic resin, a fluorine resin, and a silicon resin. In addition, various amide compounds such as stearic acid amide, oleic acid amide, and fumaric acid amide are added as organic lubricants, various antioxidants, various weathering agents such as tinuvin, and various flame retardants such as phosphorus and bromine are added. You can do it.

The film according to the present invention needs to be stretched biaxially. The film configuration may be a single film, or a laminate of two or more layers,
The resin to be laminated is not particularly limited, but a polyester resin such as polyethylene terephthalate and polyethylene-2,6-naphthalate, and a resin composition of the polyester and the polyimide are suitable from the viewpoint of a balance between cost and quality.

The biaxially oriented film of the present invention preferably has a single glass transition temperature (Tg). Whether the film has a single Tg is determined by differential scanning calorimetry,
It is determined appropriately using various analyzes such as dynamic viscoelasticity measurement. When it is difficult to judge by a method based only on solid physical properties, a morphological method such as microscopic observation may be used in combination. When Tg is determined by differential scanning calorimetry, it is effective to use a temperature modulation method or a high sensitivity method. In this case,
5 m reversible specific heat change detected by differential scanning calorimetry
Glass transition temperatures below J / g / ° C are ignored. Further, in this determination, the sheet-like material has two or more glass transitions, the polyester and the polyimide are not sufficiently compatible in the film, and the polyester, the polyimide and the thermally decomposed product or the reaction thereof are contained in the film. It should be noted that if there are a large number of dispersed domains composed of substances or the like, it becomes difficult to obtain a high-quality film disclosed in the present invention. When the film has two or more glass transition temperatures, the glass transition temperature in the present invention is a glass transition temperature on a lower temperature side. The glass transition temperature of the film is preferably 110 ° C. or more and 150 ° C. or less from the viewpoint of achieving both processing characteristics and long-term heat resistance.
The temperature is more preferably 0 ° C or more and 145 ° C or less.

In the present invention, the elongation at break in the longitudinal direction of the film is preferably 70% or more and 150% or less,
It is more preferably 85% or more and 120% or less. When the elongation at break in the longitudinal direction is out of this range, there is a tendency that processing characteristics are deteriorated and long-term heat resistance is deteriorated.

The thickness of the film of the present invention can be appropriately determined according to the purpose, but is preferably 10 μm or more and 500 μm or less, and more preferably 25 μm or more and 300 μm or less. When the thickness of the film is less than 10 μm, the electrical insulation is insufficient. On the other hand, when the thickness is more than 500 μm, the film becomes hard and the workability is poor.

The film of the present invention has a density of 1.37 g from the viewpoint of compatibility between processing characteristics and long-term heat resistance.
/ Cm ³ or more and less than 1.41 g / cm ³ . It should be noted that if the density of the film exceeds these ranges, the effects of the present invention are hardly obtained.

The Young's modulus of the film of the present invention is preferably 3.5 GPa or more and 6.0 GPa or less in both the longitudinal direction and the width direction from the viewpoint of processing characteristics and long-term heat resistance. A more preferable range of the Young's modulus is 3.8 GPa or more and 5.5 GPa or less. Young's modulus is 3.5 GPa
If the value is less than the above range, the insertability of the film is insufficient. Conversely, if the Young's modulus exceeds 6.0 GPa, it should be noted that the brittleness and fibrousness of the film are reduced and the handling property is deteriorated.

The film according to the present invention as described above can be manufactured, for example, by the following method.

A method such as addition at the time of polymerization, addition at the time of melt-kneading, or mixing of a high-concentration master material is appropriately combined,
Further, a resin composition containing polyester as a main component and polyimide is prepared by adding predetermined particles and additives as needed. This resin composition was treated with a water content of 70
ppm or less, preferably after drying to 50 ppm or less,
It is melted using an extruder, extruded into a sheet using a die, and cooled on a cooling roll at 30 to 100 ° C. At this time, the polyester raw material used has an intrinsic viscosity of 0.80 dl / g or more and 1.2
dl / g or less, and the content of the cyclic trimer in the polymer is preferably reduced to 0.5% by weight or less, more preferably 0.45% by weight or less. In addition, in the melt extrusion when forming into a film, a barrier flight type screw that is effective in separating the solid phase and the liquid phase until the polymer is completely melted is used, suppressing shear heat generation during melting, It is effective to control the temperature within a temperature range of 290 to 310 ° C. and perform melt molding with a residence time of 5 minutes or less in obtaining the film of the present invention. Also, when a blended chip of polyester and polyimide is prepared using a twin-screw kneader, it is important to set the same extrusion conditions as described above, shorten the residence time as much as possible, and suppress oligomer regeneration. It is. Here, the residence time is a value obtained by dividing the total volume of the extrusion system by the discharge amount. When an extruder having a vent hole is used, the drying step may be omitted.

Next, the obtained sheet is stretched in the longitudinal direction (longitudinal direction) and then in the width direction (horizontal direction), or after stretching in the width direction (horizontal direction). The film is given a biaxial orientation by a sequential biaxial stretching method or a simultaneous biaxial stretching method in which the film is stretched in the step (1). In the following, specific examples based on the most commonly used sequential biaxial stretching method will be described, but it goes without saying that the present invention is not limited to the following description.

First, a film heated by a plurality of rolls is stretched at a stretching temperature of 90 to 170 ° C., a magnification of 2 to 5 times,
Preferably, the film is stretched in the longitudinal direction (longitudinal direction) in one or two or more stages at a magnification of 2.5 to 4.0 times, and the film is gripped with a clip and guided to a tenter.
The film is stretched in the width direction (transverse direction) at a stretching temperature of １８０180 ° C. and a magnification of 2 to 5 times, preferably 2.5 to 4.0 times. In this case, if necessary, the film may be stretched 1.01 to 2.5 times in the longitudinal direction and / or the width direction at 110 to 180 ° C. The heat treatment after stretching is generally 100 to 2
Although it is performed at 50 ° C., in the present invention, it is preferable that the heat treatment is performed at 210 to 235 ° C. In the cooling step after heat treatment,
It is preferable to perform a relaxation treatment, and each of vertical and horizontal is 0.1 to 7
It is preferable to perform the relaxation treatment at a percentage of%. After the completion of the heat treatment, in the temperature range of 170 to 230 ° C., the film is relaxed individually or simultaneously at a rate of 0.5% or more and 7% or less in the vertical and horizontal directions to achieve the film quality of the present invention. Is preferred. Further, the obtained roll-shaped film can be heat-treated at 70 to 120 ° C. for 1 hour to 10 days, or the heat-set film can be heat-treated again. Alternatively, the film before or after heat setting may be treated with a solvent such as xylene or chloroform to extract and remove low molecular compounds in the film, and then heat-treated again. In this way, it is possible to obtain a biaxially oriented film having a small content of the compound extracted by the refrigerant and the like, and having excellent processing characteristics and long-term heat resistance. This film is mainly used for a refrigerator motor and the like. It can be suitably used for electrical insulation.

[Measurement Method] The measurement method of each characteristic used in the description of the present invention is as follows. (1) Intrinsic viscosity [η] A value calculated from the solution viscosity measured in orthochlorophenol at 25 ° C. by the following equation was used. ηsp / C = [η] + K [η] ² · C, where ηsp = (solution viscosity / solvent viscosity) −1,
C is the weight of the dissolved polymer per 100 ml of solvent (g / 1
00 ml, usually 1.2), and K is the Haggins constant (0.34
3). The solution viscosity and the solvent viscosity were measured using an Ostwald viscometer. The unit is indicated by [dl / g]. (2) Glass transition temperature The specific heat was measured by the pseudo-isothermal method using the following equipment and conditions.
The glass transition temperature was determined according to JIS K7121. Apparatus: Temperature modulated DSC manufactured by TA Instrument Measurement conditions: Heating temperature: 270 to 570K (RCS cooling method) Temperature calibration: Melting point of high-purity indium and tin Temperature modulation amplitude: ± 1K Temperature modulation cycle: 60 seconds Temperature rise step: 5K Sample weight: 5 mg Sample container: aluminum open container (22 mg) Reference container: aluminum open container (18 mg) The glass transition temperature was calculated by the following equation. Glass transition temperature = (extrapolated glass transition start temperature + extrapolated glass transition end temperature) / 2

(3) Young's modulus and elongation at break According to JIS-K-7127. Using an Instron type tensile tester, measurement was performed at 20 ° C. and 65% RH using a sample film having a sample length of 50 mm and a sample width of 10 mm. The elongation at break is pulled until the film breaks when a tensile test is performed, and the elongation at break of the film is read,
Expressed as a percentage of the film length before measurement. (4) Content of cyclic trimer 100 mg of a film was dissolved in 1 ml of orthochlorophenol, and the solution was subjected to liquid chromatography (Model 8500 Varian (product)).
And expressed as a ratio (% by weight) to the total weight of the film.

(5) Amount of element contained in polyester, M
/ P Li was measured by an atomic absorption method [AA630-13 type (manufactured by Shimadzu Corporation)]. For other elements,
Fluorescent X-ray method [IKF 3064 type (manufactured by Geigerflex)]
Was measured by From these measurement results, the ratio of the metal compound to the phosphorus compound (M / P) was determined. (6) Processing Characteristics A film was cut out so as to have a length of 40 mm in the longitudinal direction of the film and a width of 20 mm in the width direction, and then both ends were turned back by 5 mm each in parallel with the width direction to prepare a motor insertion sample. This sample was inserted into the motor rotor, and the enameled wire was wound. Thereafter, the enameled wire was pressed to mold the enameled wire, and at this time, the occurrence of cracks in the film sample was evaluated. The measurement was performed on 10 film samples, and the judgment was made based on the following criteria. ：: No cracks are generated. Δ: One or two samples are cracked. ×: Three or more samples cracked.

(7) Long-term heat resistance (half-life of elongation at break)
[Time] Measure according to UL746B. Specifically, the film before the heat treatment is cut out in the longitudinal direction, and the elongation at break is measured with a Tensilon type tensile tester to determine the initial elongation at break. This film is heat-treated in an atmosphere of 190 ° C. in a heating oven, and the time required for the elongation at break in the longitudinal direction to decrease to の of the initial elongation at break is determined.

[0040]

EXAMPLES Specific examples of the present invention will be described below in comparison with comparative examples.

Example 1 0.09% by weight of calcium acetate and 0.03% by weight of antimony trioxide based on dimethyl terephthalate were added to a mixture of dimethyl terephthalate and ethylene glycol, and heated by a conventional method. The transesterification reaction was performed by heating. Next, after adding 0.15% by weight of lithium acetate and 0.21% by weight of trimethyl phosphate with respect to dimethyl terephthalate as a raw material to the obtained transesterification reaction product, the mixture was transferred to a polymerization reaction tank, Then, the reaction system was gradually depressurized while heating and heated, and polymerized by a conventional method at 290 ° C. under a reduced pressure of 1 mmHg to obtain polyethylene terephthalate (PET) having an intrinsic viscosity of 0.54 dl / g. The obtained PET polymer was cut into a cube having a diameter of 3 mm, and heated at 225 ° C. for 35 hours under a reduced pressure of 1 mmHg using a rotary vacuum polymerization apparatus to obtain a PET polymer having an intrinsic viscosity of 0.85 dl / g. Obtained. As a result of analyzing the amount of elements contained in the PET, Ca = 200 (ppm), L
i = 100 (ppm), P = 350 (ppm), and M / P
= 1.0. The content of the cyclic trimer is 0.3
It was 2% by weight.

The P having an intrinsic viscosity of 0.85 dl / g obtained here
30 parts by weight of 50 parts by weight of ET and 50 parts by weight of polyetherimide “Ultem 1010” manufactured by GE Plastics
The mixture was put into a vented twin-screw kneader heated to 0 ° C., and PET / polyetherimide was reduced to 50/50 with a residence time of 2 minutes.
(Weight ratio) blend chips were prepared.

Next, 20 parts by weight of the obtained blend chip and 80 parts by weight of the above-mentioned PET chip having an intrinsic viscosity of 0.85 dl / g were mixed and dried to a water content of 30 ppm or less. Into a 120 mm single screw extruder equipped with a screw, controlled the polymer temperature at 290 ° C., melted and kneaded with a residence time of 3 minutes, extruded into a sheet, and cooled on a cooling roll at 20 ° C. . 3.4 times the sheet at 105 ° C. in the longitudinal direction,
After stretching 3.7 times in the width direction at 110 ° C, 210 ° C
After a 3% relaxation treatment in the width direction at 170 ° C., the film was cooled to room temperature and wound up to obtain a biaxially oriented film having a thickness of 100 μm. Table 1 shows the raw materials and film forming conditions. Table 2 shows the properties of the obtained film. The film obtained in this example had a single glass transition temperature, was a low oligomer, and had excellent processing characteristics and long-term heat resistance.

Examples 2 to 4, Comparative Examples 1 and 2 A film was formed in the same manner as in Example 1 except that the polyimide content was changed and the film was formed under the conditions shown in Table 1. An axially oriented film was obtained. Table 1 shows the properties of the obtained film. When the addition amount of the polyimide was within the preferred range, a film having a low oligomer and excellent long-term heat resistance and processing characteristics was obtained. The film of Comparative Example 1 consisting of PET alone containing no polyimide, and the polyimide content was 5%
The film of Comparative Example 2, which was less than that, had a larger amount of oligomers than the film of Example 1 and was inferior in terms of long-term heat resistance. The film of Example 4 in which the polyimide content was 45% by weight had good heat resistance, but the processing characteristics were not at a sufficient level.

[Comparative Examples 3 and 4] The amount of trimethyl phosphate added was 0.13% by weight in Comparative Example 3 and 0.4 in Comparative Example 4.
M / P in PET was changed by changing to 5% by weight, and a film was formed in the same manner as in Example 1 except that the film was formed under the conditions shown in Table 1 to obtain a biaxially oriented film having a thickness of 100 μm. Was.
When the M / P in PET is out of the preferred range, the amount of oligomer increases, and the low oligomer,
A film satisfying both long-term heat resistance and processing characteristics could not be obtained.

Comparative Example 5 A film was formed in the same manner as in Example 1 except that the screw of the extruder was changed to a normal full flight type and the melt extrusion conditions were changed as shown in Table 1 to form a film. A biaxially oriented film having a thickness of 100 μm was obtained. In this comparative example, the amount of oligomer regeneration increased remarkably, and the film of the present invention was not obtained.

Example 5 100 parts by weight of dimethyl-2,6-naphthalate, 60 parts by weight of ethylene glycol and 0.09 part by weight of magnesium acetate tetrahydrate were placed in a reactor, and the temperature was raised to 230 ° C. over about 4 hours. The temperature was gradually raised. The methanol produced at this time was distilled off, and the transesterification reaction was terminated. To this reaction product were added 0.04 part by weight of trimethyl phosphate, 0.03 part by weight of antimony trioxide, and 0.3 part by weight of titanium oxide having an average particle diameter of 0.3 μm dispersed in 10 parts by weight of ethylene glycol. Polymerization was performed according to the method to obtain a polyethylene naphthalate (PEN) chip having an intrinsic viscosity of 0.48. This chip is 200
Solid phase polymerization was performed at 30 ° C. for 30 hours to obtain a PEN chip having an intrinsic viscosity of 0.75 and a cyclic trimer content of 0.38% by weight.

The intrinsic viscosity obtained here is 0.75 dl / g.
50 parts by weight of PEN and 50 parts by weight of polyetherimide “Ultem 1010” manufactured by GE Plastics
The mixture was charged into a vent-type twin-screw kneader heated to 305 ° C., and the PEN / polyetherimide was removed at a residence time of 2 minutes.
/ 50 (weight ratio) blend chips were prepared.

Next, 20 parts by weight of the obtained blend chip and 80 parts by weight of the above-mentioned PEN chip having an intrinsic viscosity of 0.75 dl / g were mixed and dried to a water content of 30 ppm or less. Into a 120 mm single screw extruder equipped with a screw. The polymer temperature was controlled at 300 ° C., the mixture was melted and kneaded with a residence time of 3 minutes, extruded into a sheet, and cooled on a cooling roll at 20 ° C. The sheet is stretched 3.7 times in the longitudinal direction at 138 ° C, and further stretched 3.8 times in the width direction at 145 ° C.
The sample was heat-set at 5 ° C. for 5 seconds, and then gradually cooled to room temperature and wound up. At this time, the film thickness was 100 μm.
Table 2 shows the properties of the obtained film. The film obtained here had lower oligomers and better long-term heat resistance and processing characteristics than the film of Comparative Example 7 consisting of PEN alone.

Comparative Example 6 A biaxially oriented film having a thickness of 100 μm was obtained in the same manner as in Example 4 except that PEI was not added and the film was formed under the conditions shown in Table 1. Table 2 shows the properties of the obtained film.

[Embodiment 6] Here, an example using a polyimide other than PEI will be described. Polyimide A used in this example was polymerized by the following production method.

Under a nitrogen atmosphere, 200 g of isophorone diisocyanate was added to N-methyl-2-pyrrolidone (NMP) 3
Add to 000 ml and stir. Next, after adding 196 g of pyromellitic anhydride to this solution at room temperature, the temperature is gradually raised. Thereafter, when heating was performed at 180 ° C. for 6 hours, the generation of carbon dioxide was terminated, so the heating was stopped. This polymer solution was developed in water and washed, and then the obtained polymer was dried.

A film was formed in the same manner as in Example 1 under the film forming conditions shown in Table 1 except that the obtained polyimide A (PIA) was used in place of polyetherimide.
A μm biaxially oriented film was obtained. Table 2 shows the properties of the obtained film. Although the amount of oligomer was slightly increased as compared with the case where polyetherimide was used, the film of this example was also low in oligomer and excellent in long-term heat resistance and processing characteristics.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

The biaxially oriented film of the present invention is a low oligomer and has excellent long-term heat resistance and processing characteristics.
It is useful as an electrical insulating film, particularly as an electrical insulating film in a refrigerator motor field where a low oligomer is required.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08L 79:08) C08L 79:08) B29K 67:00 B29K 67:00 79:00 79:00 105: 34 105: 34 B29L 7:00 B29L 7:00 F term (reference) 4F210 AA24 AA26 AA40 AG01 AH33 QC05 QG01 QG18 QW06 QW12 4J002 CF061 CF081 CM042 GQ01 5G305 AA20 AB24 AB36 BA19 CA11 CA21 CB28 DA13 5G333 AA03 AB07

Claims (7)

[Claims] 1. A film comprising a resin composition containing a polyester as a main component and a polyimide, wherein the content of the cyclic trimer is 0.1% by weight or more and 0.5% by weight or less. Biaxially oriented film for electrical insulation. 2. A glass transition temperature of 110 ° C. or more, 150
The biaxially oriented film for electrical insulation according to claim 1, wherein the temperature is lower than or equal to ° C. 3. The elongation at break in the longitudinal direction of the film is 70%.
The biaxially oriented film for electrical insulation according to claim 1 or 2, wherein the content is 150% or less. 4. A polyimide content of 5% by weight or more,
The biaxially oriented film for electrical insulation according to any one of claims 1 to 3, wherein the content is 5% by weight or less. 5. The polyester according to claim 1, wherein the polyester is polyethylene terephthalate, polyethylene-2,6-naphthalate, a copolymer or a modified product thereof.
5. The biaxially oriented film for electrical insulation according to any one of items 1 to 4. 6. The biaxially oriented film for electrical insulation according to claim 1, wherein the polyimide is a polyetherimide. 7. A film having a thickness of 10 μm or more and 500
The biaxially oriented film for electrical insulation according to any one of claims 1 to 6, wherein the thickness is not more than μm.