JP2002273844A - Biaxially oriented laminated polyester film for electric insulation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented laminated polyester film for electric insulation capable of preventing the generation of the problem caused by ply separation or an adhesive while keeping the excellent thermal deterioration resistance and oligomer suppressing effect of polyethylene-2,6-naphthalate. SOLUTION: The biaxially oriented laminated polyester film for electric insulation is constituted by laminating layers (surface layers) comprising polyethylene-2,6-naphthalenedicarbolxylate on both surfaces of a layer (intermediate layer) comprising polyethylene terephthalate. The intermediate layer contains 0.05-<15 wt.% of the polyethylene-2,6-naphthalenedicarbolxylate component, and the part of at least 1 μm from both surfaces thereof in a thickness direction contains 1-<30 wt.% or >70-99 wt.% of the polyethylene-2,6- naphthalenedicarbolxylate. Each of the surface layers has a thickness of at least 2 μm and is below 10% on the basis of the thickness of the laminated film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated polyester film for electrical insulation, and more particularly, it is suitable for slot insulation and a wedge of a refrigerator motor. The present invention relates to a biaxially oriented laminated polyester film for electrical insulation which is difficult to delamination.

[0002]

2. Description of the Related Art Biaxially oriented polyethylene terephthalate films and processed products thereof are mainly used as electric insulating films. In recent years, biaxially oriented polyethylene-2,6 has more excellent heat deterioration resistance and less oligomer extraction amount.
-Naphthalene dicarboxylate films have also been used. These films have the following properties: they are mechanically degraded and brittle when exposed to high temperatures for a long period of time; insulation performance is not deteriorated and insulation breakdown characteristics are not impaired; It is required that lamination does not occur and that low-molecular-weight substances (oligomers) extracted from the film surface into a refrigerant or the like are small. This is particularly important when used for equipment that uses an insulating material in a refrigerant, such as a refrigerator motor.

[0003] In order to improve the heat deterioration resistance of a biaxially oriented polyethylene-2,6-naphthalenedicarboxylate film and to suppress the amount of extracted oligomers, it is effective to increase the draw ratio to improve the molecular orientation. This method has been adopted. However, this method has a new problem that the film tends to be delaminated as a result of improving the plane orientation, and there is a limit in increasing the draw ratio. In order to make the delamination less likely to occur, there is a method of lowering the plane orientation contrary to the above method. However, this results in a decrease in heat deterioration resistance and an increase in oligomer generation.

Japanese Patent Application Laid-Open No. 11-92577 also proposes a laminated film in which polyethylene-2,6-naphthalate having excellent thermal stability is laminated on both sides of polyethylene terephthalate via an adhesive such as heat-resistant polyurethane. ing. However, in addition to the problem that the adhesive itself is easily extracted by the refrigerant and the like, the effect of causing polyethylene-2,6-naphthalate to be present in the surface layer is impaired, and that the surface layer is liable to peel off over time due to deterioration of the adhesive. There were also problems.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems caused by delamination and adhesives while maintaining the excellent heat-resistant deterioration and oligomer-suppressing effects of polyethylene-2,6-naphthalate. An object of the present invention is to provide a film for electric insulation which is particularly suitable for use in a refrigerant for electric insulation.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have found that polyethylene-2,
If polyethylene terephthalate in which a 6-naphthalenedicarboxylate film is disposed on the surface and polyethylene-2,6-naphthalenedicarboxylate is contained in the intermediate layer at a specific ratio is used, it is resistant even without an adhesive or the like. The present inventors have found that an electrical insulating film having a low oligomer extraction amount can be obtained while having excellent delamination properties, and the present invention has been achieved.

Thus, according to the present invention, there is provided a laminated film in which a layer (surface layer) composed of polyethylene-2,6-naphthalenedicarboxylate is laminated on both surfaces of a layer (intermediate layer) composed of polyethylene terephthalate, The layer contains not less than 0.05% by weight and less than 15% by weight of an ethylene-2,6-naphthalenedicarboxylate component, and at least 1 μm in the thickness direction from both surfaces thereof (intermediate layer surface portion) is ethylene-containing. The composition contains a 1,6-naphthalenedicarboxylate component in an amount of 1% by weight or more and less than 30% by weight or more than 70% by weight and 99% by weight or less, and each surface layer has a thickness of at least 2 μm.
As described above, there is provided a biaxially oriented laminated polyester film for electrical insulation, wherein the thickness of each surface layer is less than 10% based on the thickness of the laminated film.

[0008] According to the present invention, as a preferred embodiment of the present invention, the electrical insulation board having a peel resistance between the intermediate layer and the surface layer of the laminated film of at least 10 as evaluated by JIS K5400-1990 is preferred. Axial orientation laminated polyester film, at least one surface center line average roughness (R
a) a biaxially oriented laminated polyester film for electrical insulation having a haze value of at least 20 in the range of 5 to 50 nm;
% Biaxially oriented laminated polyester film for electrical insulation, wherein the intermediate layer contains 0.1 to 1% by weight of titanium dioxide particles having an average particle size of 0.01 to 0.5 μm. Is also provided.

Further, according to the present invention, the biaxially oriented laminated polyester film for electrical insulation of the present invention comprises a polyethylene-2,6-naphthalenedicarboxylate having polyethylene-2,6-naphthalenedicarboxylate on both sides of a molten polymer mainly comprising polyethylene terephthalate. It is preferably a biaxially oriented laminated polyester film obtained by co-extrusion of a polymer in a molten state mainly comprising

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The biaxially oriented laminated polyester film for electrical insulation of the present invention has a layer mainly composed of polyethylene-2,6-naphthalenedicarboxylate on both surfaces of a layer mainly composed of polyethylene terephthalate (intermediate layer). (Surface layer) is a laminated film composed of at least three layers laminated. The above-mentioned intermediate layer contains polyethylene-2,6-naphthalenedicarboxylate in 0.1%.
The intermediate layer portion (intermediate layer surface portion), which is contained in an amount of at least 1% by weight in the thickness direction, is made of polyethylene-2,6 in a thickness direction of at least 1 μm.
-It is necessary to contain naphthalenedicarboxylate in an amount of 1% by weight or more and less than 30% by weight. In addition, each surface layer has a thickness of 2 μm or more, and the ratio of the thickness of each surface layer is based on the thickness of the laminated film.
It needs to be less than 10%.

The biaxially oriented laminated polyester film for electrical insulation of the present invention will be described in detail below.

[Surface Layer] In the biaxially oriented laminated polyester film for electrical insulation of the present invention, the polyester forming both surface layers is mainly composed of polyethylene-2,6-naphthalenedicarboxylate. Specifically, it refers to a polymer in which a component having ethylene-2,6-naphthalenedicarboxylate as a repeating unit is 97 mol% or more, and preferably 99 mol% or more. Examples of the copolymerization component include compounds having two ester-forming functional groups, such as oxalic acid, adipic acid, phthalic acid, sebacic acid, dodecanedicarboxylic acid, succinic acid, 5-sodium sulfoisophthalic acid, terephthalic acid, and isophthalic acid. Acid, 2-potassium sulfoterephthalic acid, 2,7-naphthalenedicarboxylic acid,
1,4-cyclohexanedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, phenylindanedicarboxylic acid,
Diphenyl ether dicarboxylic acid and lower alkyl esters thereof, oxycarboxylic acids such as p-oxyethoxy benzoic acid and lower alkyl esters thereof, propylene glycol, 1,2-propanediol, 1,3-
Butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-
Cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,4-cyclohexane dimethanol,
Examples thereof include p-xylylene glycol, an ethylene oxide adduct of bisphenol A, an ethylene oxide adduct of bisphenol sulfone, triethylene glycol, polyethylene oxide glycol, polytetramethylene oxide glycol, neopentyl glycol and the like. Among these, a copolymer polyester obtained by copolymerizing isophthalic acid with 1 to 3 mol% is preferable, and a film made of a homopolymer of polyethylene-2,6-naphthalenedicarboxylate is particularly preferable.

Further, in the present invention, polyethylene-
The polymer containing 2,6-naphthalenedicarboxylate as a main component preferably has a copolymerization amount of a diethylene glycol component of 3 mol% or less (based on all glycol components). This diethylene glycol component is by-produced during the production reaction even if it is not added as a copolymer component during the production of the polymer. If the copolymerization amount of the diethylene glycol component exceeds 3 mol%, the effect of improving the layered peeling resistance when formed into a film increases, but the crystallinity of the polymer is impaired, and the mechanical strength is greatly reduced. The copolymerization ratio of the diethylene glycol component is preferably 2.5 mol% or less, more preferably 2 mol% or less. In order to suppress the by-product of diethylene glycol during the production reaction, the molar amount of ethylene glycol as a raw material should be increased in the range of 2.0 to 3.0 times the molar amount of dicarboxylic acid, and the transesterification should be as small as possible. It is preferable to reduce the time required for the reaction. The polyethylene-2,6-naphthalenedicarboxylate is obtained by blocking a part or all of the terminal hydroxyl group and / or carboxyl group with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol. Or a small amount such as glycerin, pentaerythritol, etc.
It may be modified with a functional or higher functional ester-forming compound within a range in which a substantially linear polymer can be obtained.

The polyethylene-2,6-naphthalenedicarboxylate is obtained, for example, by subjecting the above-mentioned ethylene glycol to a transesterification reaction with dimethyl 2,6-naphthalenedicarboxylate, and then subjecting the obtained esterified product to polycondensation. It is obtained by reacting. In this case, a manganese compound is preferable as the transesterification catalyst, and examples of the manganese compound include oxides, chlorides, carbonates, and carboxylate salts. Of these, acetate is particularly preferably used. It is preferable to add a phosphorus compound at the time when the transesterification reaction is substantially completed to deactivate the transesterification catalyst. As the phosphorus compound, trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate and orthophosphoric acid can be preferably used, and among these, trimethyl phosphate is particularly preferable. As the polycondensation catalyst, an antimony compound is preferably used, and as the antimony compound, antimony trioxide is particularly preferably used.

In the present invention, a manganese compound, a phosphorus compound and an antimony compound are used to prepare polyethylene-2,
When producing 6-naphthalenedicarboxylate,
These catalysts and catalyst deactivators are represented by the following general formula (1):
It is preferable to contain them in amounts satisfying (2) and (3).

[0016]

(1) 30 ≦ Mn ≦ 100 (1)

[0017]

[Equation 2] 150 ≦ Sb ≦ 450 (2)

[0018]

P / Mn ≧ 1 (3) where Mn is the amount of manganese element in polyethylene-2,6-naphthalenedicarboxylate (pp
m) and Sb represent the amount (ppm) of antimony element in polyethylene-2,6-naphthalenedicarboxylate, and P represents the amount (ppm) of phosphorus element in polyethylene-2,6-naphthalenedicarboxylate.

When the content of the manganese element in the polyethylene-2,6-naphthalenedicarboxylate is less than 30 ppm, the transesterification is insufficient, while
If it exceeds PPm, the volume resistivity of the film may decrease, and the film may not be suitable as an electrical insulating film. Also,
When the content of the antimony element is less than 150 ppm, the polycondensation reactivity decreases and the productivity is deteriorated.
If the ratio exceeds the above range, the thermal stability is poor, and the process may be cut during film formation or the mechanical strength may be reduced. Furthermore, P / M
If n is less than 1, the intrinsic viscosity may decrease.

The polyethylene-2,6- used in the present invention
The content of the alkali metal in the naphthalenedicarboxylate is preferably 10 ppm or less. When the content of the alkali metal exceeds 10 ppm, the volume resistivity of the film decreases, and the film may not be suitable as an electrical insulating film.

Incidentally, the laminated film of the present invention has a film surface center line average roughness (Ra) of at least one side of 3
It is preferably from 50 to 50 nm, particularly preferably from 5 to 20 nm. If the surface roughness Ra is less than 3 nm, the slip between the films is poor and good winding cannot be performed. On the other hand, if the surface roughness Ra exceeds 50 nm, the layer itself (not the interface peeling with another layer, but this layer itself) Peels off)
Is more likely to occur. Such surface center line average roughness (R
To achieve a), the polyethylene forming the surface layer
Preferably, 2,6-naphthalenedicarboxylate contains a small amount of inert particles. Examples of such inert particles include inorganic particles such as spherical silica, porous silica, calcium carbonate, silica alumina, alumina, titanium dioxide, kaolin clay, barium sulfate, and zeolite, or organic particles such as cross-linked silicone resin particles and cross-linked polystyrene particles. Particles can be given. Inorganic particles are more natural than natural products due to their uniform particle size.
It is preferably a synthetic product, and inorganic particles of any crystal form, hardness, specific gravity, and color can be used.

The above-mentioned inert fine particles have an average particle size of 0.05.
３3.0 μm, preferably 0.1-3.0 μm.
More preferably, it is 2.0 μm. Further, the content of the inert fine particles is preferably from 0.001 to 1.0% by weight, and more preferably from 0.03 to 0.5% by weight. The inert particles to be added to the film may be a single-component system selected from those exemplified above or a multi-component system containing two or more components.

The inert particles are added at the time of polyethylene-
There is no particular limitation as long as it is a stage before the 2,6-naphthalenedicarboxylate film is formed. For example, it may be added at the polymerization stage or may be added at the time of film formation.

In the present invention, the thickness of each surface layer needs to be 2 μm or more, and preferably 3 μm or more.
When the thickness of the surface layer is less than 2 μm, a large amount of oligomer is extracted into the refrigerant, and the refrigerant vaporization nozzle may be clogged,
Not suitable for motor insulation for refrigerators. On the other hand, the thickness of the surface layer is at most 10 based on the total thickness of the entire laminated film.
%, Preferably 7% or less. If the thickness of the surface layer exceeds 10% of the total thickness of the entire laminated film, laminar peeling and cracking during processing will increase. For example, when the total thickness of the entire laminated film is 188 μm,
The thickness of each surface layer is at most 18.8 μm.

[Intermediate Layer] The intermediate layer constituting the biaxially oriented laminated polyester film of the present invention contains polyethylene terephthalate as a main component, and the intermediate layer as a whole contains ethylene-2,6-naphthalenedicarboxylate as 0%. It must be contained at least 0.05% by weight and less than 15% by weight. Ethylene-2,6- contained in the entire intermediate layer
The content of the naphthalenedicarboxylate component is 0.05
When the content is less than 15% by weight, peeling easily occurs at the interface between the surface layer and the intermediate layer or in the intermediate layer. On the other hand, when the content is 15% by weight or more, the crystallinity of the entire intermediate layer is poor and the strength of the entire laminated film is low. Tends to decrease.

A portion of the intermediate layer adjacent to the surface layer (intermediate layer surface portion), that is, a region at least 1 μm from the surface of the intermediate layer in the thickness direction is ethylene-2,
6-naphthalenedicarboxylate component in an amount of 1% by weight or more and less than 30% by weight or more than 70% by weight and 99% by weight or less, preferably 3 to 25% by weight or 75 to 97% by weight.
contains. Ethylene-2,6- at the surface of the intermediate layer
1% by weight of naphthalenedicarboxylate component
If it is less than 99% by weight or more than 99% by weight, peeling is likely to occur at the interface between the surface layer and the intermediate layer or in the intermediate layer. On the other hand, when the content is more than 30% by weight or 70% by weight or less, The crystallinity is significantly reduced, and the strength of the entire laminated film is reduced. Further, if the thickness of the surface portion of the intermediate layer is less than 1 μm, peeling is likely to occur at the interface between the surface layer and the intermediate layer.

As the intermediate layer satisfying the content of the ethylene-2,6-naphthalenedicarboxylate component, the ethylene-2,6-naphthalenedicarboxylate component is contained in an amount of 1% by weight to 30% on the surface of the intermediate layer. Polyethylene terephthalate containing less than 70% by weight or less than 70% by weight and 99% by weight or less, and the content of ethylene-2,6-naphthalenedicarboxylate in the intermediate layer excluding the surface of the intermediate layer is reduced to 0%. A very small amount of polyethylene terephthalate may be used, such as at most 15 wt.
The intermediate layer consists of at least three layers. Of course, the intermediate layer may be a single layer, in which case the intermediate layer contains one component of ethylene-2,6-naphthalenedicarboxylate.
Polyethylene terephthalate containing not less than 15% by weight and not more than 15% by weight may be used. From the viewpoint that the production process can be simplified, the latter intermediate layer is preferably a single layer, and the point that the strength of polyethylene terephthalate is easily developed to a high degree. It is preferable that the central portion substantially consists of polyethylene terephthalate homopolymer.

The term “content” as used in the present invention may be a copolymer or a mixture, and is preferably a copolymer. ethylene-
The means for mixing or copolymerizing the 2,6-naphthalenedicarboxylate component with the polyethylene terephthalate is not limited at all, but the unfinished portion of the laminated film of the present invention is pulverized, dried, re-melted in a clean room of a factory. Preferably, it is used as cut pellets. Recycled products processed in a clean room have the same cleanliness as new products.
It is desirable to use it also for effective use of resources. However, it is advisable to add new polyethylene terephthalate since the degree of polymerization is somewhat reduced. Thus, when remelting is repeated, the polyethylene terephthalate and the ethylene-2,6-naphthalenedicarboxylate component are almost copolymerized.

By the way, in the present invention, that the intermediate layer is made of polyethylene terephthalate means that the ethylene terephthalate component accounts for 80% by weight or more of the intermediate layer. The polyethylene terephthalate constituting the intermediate layer may be a copolymer of other components as long as the content of the ethylene-2,6-naphthalenedicarboxylate component is within the above range. As the copolymer component,
It may be a dicarboxylic acid component or a diol component. As the dicarboxylic acid component, aromatic dicarboxylic acids such as isophthalic acid and phthalic acid; adipic acid, azelaic acid, sebacic acid, and aliphatic dicarboxylic acids such as decanedicarboxylic acid;
Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be exemplified. Examples of the diol component include aliphatic diols such as 1,4-butanediol, 1,6-hexanediol, and diethylene glycol, and 1,4-cyclohexanedimethanol. Examples thereof include alicyclic diols such as the above, and aromatic diols such as the bisphenol A. These can be used alone or in combination of two or more. Of these, copolymers of isophthalic acid are preferred because of their high tear strength, and the copolymerization amount is preferably at most 3 mol% because the thermal shrinkage is not excessively increased.

The proportion of the copolymer component depends on the type thereof, but is preferably such that the melting point of the polymer is at least 250 ° C. If the melting point is less than 250 ° C., the heat resistance will be poor. The melting point of the polyethylene terephthalate homopolymer is usually 258 ° C. Here, the melting point of a polyester containing polyethylene terephthalate as a main component was measured by Du Pont Inst.
temperature 910 DSC with a heating rate of 20
Depends on the method of determining the melting peak at ° C / min. The sample amount is about 20 mg.

Intrinsic viscosity of polyethylene terephthalate constituting the intermediate layer (orthochlorophenol, 35 ° C.)
Is preferably 0.52 to 1.50, more preferably 0.57 to 1.00, and particularly preferably 0.6 to 1.50.
0 to 0.80. If the intrinsic viscosity is less than 0.52, the tear strength may be insufficient, while if the intrinsic viscosity exceeds 1.50, productivity in the raw material production step and the film forming step may be impaired.

The polyethylene terephthalate homopolymer or copolymerized polyethylene terephthalate constituting the intermediate layer used in the present invention is not limited by the production method, but terephthalic acid and ethylene glycol are further copolymerized in the case of a copolymerized polyester. The polymerization component is added to carry out an esterification reaction, and then the resulting reaction product is subjected to a polycondensation reaction until the intended degree of polymerization is reached to obtain polyethylene terephthalate or copolymerized polyethylene terephthalate, or dimethyl terephthalate and ethylene glycol. In the case of a copolymerized polyester, a copolymerization component is further added to carry out a transesterification reaction, and then the obtained reaction product is subjected to a polycondensation reaction until the intended degree of polymerization is reached, thereby obtaining polyethylene terephthalate or copolymerized polyethylene terephthalate. It may be the over door. In addition, the polyethylene terephthalate and copolymerized polyethylene terephthalate obtained by the above method (melt polymerization) are optionally subjected to a solid state polymerization method (solid state polymerization),
Further, a polymer having a high degree of polymerization may be used. Incidentally, the copolymerized polyester, if necessary, an antioxidant,
Additives such as heat stabilizers, viscosity modifiers, plasticizers, hue improvers, lubricants and nucleating agents can be added. The catalyst used in the polycondensation reaction includes an antimony compound (S
b compound), a titanium compound (Ti compound), a germanium compound (Ge compound) and the like.

By the way, it is preferable to add fine particles of lubricant to polyethylene terephthalate constituting the intermediate layer to secure the opacity of the film. As the lubricant fine particles, any one can be selected. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate. Examples of the organic lubricant include silicone resin particles and cross-linked polystyrene particles. . By adding such particles, the haze value of the entire laminated film becomes 20
% Is preferable. If the haze value is less than 20%, a mistake in loading may be missed in a visual inspection after the motor slot is loaded as a slot liner or wedge. Such a haze value is, for example, 0.1 to 0.5 μm titanium dioxide particles having an average particle size of 0.1 to 0.5 μm.
It is obtained by adding 1.0% by weight. In addition, it is preferable to avoid adding large-diameter particles exceeding the above-described range or adding a large amount of the particles, because this causes a decrease in mechanical strength and insulating properties. However, even if the haze value of the entire laminated film is less than 20%, it is not an essential defect and is included in the present invention.

Next, preferred embodiments of the biaxially oriented laminated polyester film of the present invention will be described in detail.

The biaxially oriented laminated polyester film of the present invention preferably has a measured peeling performance evaluation value of 10 or more in accordance with JIS K5400-1990 adhesion grid evaluation. It should be noted that the case of peeling not only between the layers but also within the layers according to the evaluation is regarded as delamination. If the delamination force does not satisfy this performance, it is easy to peel off during bending, and the peeled portion may be corona-discharge-degraded during use and cause a burnout accident. Such high peel resistance is
A melted polyethylene terephthalate containing an ethylene-2,6-naphthalenedicarboxylate component on the surface at the above-mentioned specific ratio and a polyethylene-2,6-naphthalenedicarboxylate constituting the above-mentioned surface layer in a melted state were laminated. After forming a film by co-extrusion in the state,
What is necessary is just to stretch in the axial direction.

The biaxially oriented laminated polyester film of the present invention preferably has a breakdown voltage (BDV) of 260 V / μm or more from the viewpoint of being an electrically insulating material. Further, the volume resistivity of the electric insulating film of the present invention is preferably 1 × 10 ¹⁵ Ω · cm or more,
More preferably, it is 1 × 10 ¹⁶ Ω · cm.

Furthermore, the thickness of the biaxially oriented laminated polyester film of the present invention is preferably 50 to 350 μm depending on the application. In particular, for motor slots, 170-350 μm for wedges,
In many cases, a film having a thickness of 100 to 250 μm is used for the slot liner and a film having a thickness of 75 to 125 μm is used for the interphase insulation.

Next, a method for producing the biaxially oriented laminated polyester film for electrical insulation of the present invention will be described in detail.
The biaxially oriented laminated polyester film for electrical insulation of the present invention can be basically produced by a conventionally known method or a method accumulated in the art. For example, it can be obtained by first producing an unoriented laminated film and then biaxially orienting the film. This unoriented laminated film is, for example, a polyethylene-2,6-naphthalenedicarboxylate layer forming both surface layers and a polyethylene terephthalate layer forming an intermediate layer laminated in a molten state of polyester or in a state of being cooled and solidified. For example, it can be manufactured by a method such as co-extrusion or extrusion lamination. Among these, co-extrusion, in which stable adhesion between each layer is easily obtained, is preferable. The co-extrusion die includes a multi-manifold die and a feed block die, and any of them can be used, but a feed block die having a long contact time of the melt of each layer is preferable.

In addition, the look-stretched laminated film laminated by the above-described method in consideration of the thickness distribution may be further made in accordance with a conventionally-produced method for producing a biaxially oriented film. it can. For example, a thickness of 150 μm
In the case of producing the above film, the polyester is melted and coextruded at a temperature of melting point (Tm: ° C) to (Tm + 70) ° C to obtain an unstretched laminated film, and the unstretched laminated film is uniaxially (generally, longitudinal). (Tg-10) to (Tg
+70) ° C (Tg: glass transition temperature of polyester) at 2.0 times or more, preferably 2.5 times or more.
The film is stretched at a magnification of 0 times or less, and then stretched at a temperature of Tg to (Tg + 70) ° C at a temperature of 2.0 times or more, preferably 2.5 times or more and 4.0 times or less in a direction perpendicular to the stretching direction. Is preferred. At this time, the area stretching ratio obtained by multiplying the stretching ratio in the vertical direction and the horizontal direction is preferably 6 times or more, and more preferably 8 to 14 times. Furthermore, the biaxially oriented film has (T
g + 70) ° C. to (Tm−10) ° C., and can be heat-set at a temperature of, for example, 180 to 250 ° C. The heat setting time is preferably 1 to 60 seconds.

In order to increase the adhesion between the film melt and the rotary cooling drum in the step of obtaining the unstretched film, there is known an electrostatic adhesion method for applying an electrostatic charge to the film melt. However, polyethylene-2,6-
Since naphthalenedicarboxylate has a high electric resistance of the melt, the above-mentioned electrostatic adhesion may be insufficient. As a countermeasure against this, as a countermeasure, the molar ratio of a bifunctional carboxylic acid component to polyethylene-2,6-naphthalenedicarboxylate It is preferable to contain 0.1 to 40 mmol% of a quaternary phosphonium sulfonate having an ester-forming functional group based on the number.

Further, in the step of obtaining the unstretched film, in the case of a film having a final thickness of 150 μm or more, the surface of the film-like molten material between the surface where the rotary cooling drum is in close contact and the surface of the film-like molten material which is exposed to the air. A cooling rate difference may occur, and a physical property difference may occur in the thickness direction. If there is such a difference in physical properties, this weakens the delamination resistance (including delamination), so that the surface of the film-like molten material exposed to air is blown with cooling air or cooled. It is preferable to contact a roller.

[0042]

The present invention will be described in more detail with reference to the following examples. In the examples, various characteristic values were measured and evaluated by the following methods. (1) Thickness of each layer A sample for section observation is cut out perpendicular to the film surface with a microtome, and the thickness of each layer is read with a graduated microscope.
The total thickness is measured with an external micrometer.

(2) Proportion of ethylene-2,6-naphthalenedicarboxylate component in polyethylene terephthalate If the thickness of the layer is less than 10 μm, the mixing ratio of polyethylene terephthalate and polyethylene-2,6-naphthalenedicarboxylate Were prepared, and each resin composition was subjected to an X-ray photoelectron spectrometer (VG).
The ratio of the benzene ring to the naphthalene ring was determined by ESCALB-200, and a calibration curve was prepared between the mixing ratio of the ethylene-2,6-naphthalene dicarboxylate component and the ratio of the benzene ring to the naphthalene ring.

Each layer of the sample film was scraped off by slicing, and the abundance ratio of benzene rings and naphthalene rings in the scraped resin composition was measured by an X-ray photoelectron spectrometer (VG, ESCALB-200). Was used to determine the proportion (% by weight) of polyethylene-2,6-naphthalenedicarboxylate in polyethylene terephthalate.

When the thickness of the layer is 10 μm or more,
Polyethylene terephthalate and polyethylene-2,6-
A resin composition was prepared in which the mixing ratio of naphthalenedicarboxylate was changed, and each resin composition was designated as JASC.
The abundance ratio of a benzene ring and a naphthalene ring was determined by FT-IR / 700 made by O, and a calibration curve was prepared between the mixing ratio of the ethylene-2,6-naphthalene dicarboxylate component and the abundance ratio of the benzene ring and the naphthalene ring.

Then, each layer of the sample film was scraped off by slicing, and the abundance ratio of benzene rings and naphthalene rings in the scraped resin composition was determined by the FT method manufactured by JASCO.
The measurement was carried out by IR / 700, and the content (% by weight) of ethylene-2,6-naphthalenedicarboxylate in polyethylene terephthalate was determined from the above-mentioned calibration curve.

(3) Density This is a value measured by a flotation method at 25 ° C. in a density gradient tube using an aqueous solution of calcium nitrate as a solvent.

(4) Amount of extracted oligomer A film (38 mm × 38 mm) was boiled in 20 cc of xylene at 139 ° C. for 2 hours, cooled slowly, and the film was taken out. The amount of oligomer in the xylene was measured at a wavelength of 240 nm.
It is determined from the absorbance of m. The relationship between the concentration of the oligomer and the absorbance was used by preparing a calibration curve in advance. The absorbance is measured using a UV-VIS-NIR spectrophotometer UV-3101PC manufactured by Shimadzu.

(5) Evaluation of Interlaminar Peeling The peeling force is evaluated by an adhesive grid evaluation according to JIS K5400-1990. The following scores are also in accordance with JIS standards. 10: There is no peeling at the intersection of the cut and the cell. 8: There is slight peeling at the intersection of cuts, and the missing part of the cells is less than 5% of all cells. 6: Peeling was found on both sides and intersections of the cut, and the missing part of the cells was more than 5% and not more than 15% of all cells. 4: The width of peeling due to cuts is wide, and the missing part of cells is more than 15% and not more than 35% of all cells. 2: The width of peeling due to cuts is wider than 4 above, and the missing part of the cells is more than 35% and 65% or less of all cells. 0: The missing part of the cells exceeds 65% of all cells. In addition, the case where it peels in a layer is also considered as the delamination force.

(6) Tensile strength and elongation Using a tensile tester (manufactured by Toyo Baldwin, Tensilon), the strength was measured at a temperature of 20 ° C. according to JIS C2318.
10m width in a room adjusted to 50% relative humidity
m, a 150 mm long strip-shaped sample (two types were prepared, one with the longitudinal direction of the sample along the film forming direction and the other with the sample width direction along the film forming direction). The sample was pulled at a chuck distance of 100 mm and a tensile speed of 10 mm / min, and the stress and elongation at break were determined from the obtained stress-strain curve. Then, the one in which the longitudinal direction of the sample was along the film forming direction and the one in which the sample width direction was along the film forming direction were measured, and the average of both was defined as the breaking stress and breaking elongation. .

(7) Workability Using a wedge-formed part of a motor processing machine manufactured by Odawara Engineering Co., Ltd.
m, a wedge of 60 mm in length, processed at a processing speed of 2 pcs / sec in an atmosphere of 25 ° C. and 50% RH, and visually inspected for delamination (including in-layer delamination) as a defective product, and occurrence of a defective product Expressed as a percentage. The number of processed samples is 20 for each sample.

Example 1 To a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 60 parts of ethylene glycol, 0.03 part of manganese acetate tetrahydrate was added.
The transesterification reaction was performed while gradually raising the temperature from 50 ° C to 240 ° C. During the reaction, when the reaction temperature reached 170 ° C., 0.024 parts of antimony trioxide was added, and 0.08% by weight of porous silica having an average particle size of 1.7 μm was added. Then, when the temperature reached 220 ° C. And 3,5-dicarboxybenzenesulfonic acid tetrabutylphosphonium salt.
042 parts (corresponding to 2 mmol%) were added. Subsequently, a transesterification reaction was performed, and after the transesterification reaction was completed, 0.023 parts of trimethyl phosphate was added. Thereafter, the reaction product was transferred to a polymerization reactor and heated to 290 ° C.
The polycondensation reaction was carried out under a high vacuum of not more than mHg, and the intrinsic viscosity measured with an o-chlorophenol solution at 25 ° C. was 0.6.
A polyethylene-2,6-naphthalenedicarboxylate polymer of 1 dl / g and a DEG copolymerization amount of 1.1 mol% was obtained. After drying this polymer at 170 ° C. for 6 hours, it is supplied to an extruder, melted at a melting temperature of 300 ° C., and has an average opening of 24 μm made of stainless fine wire having a wire diameter of 13 μm.
m and passed through the first and third layers of a three-layer extrusion die, i.e., to form both surface layers.

Separately, dimethyl terephthalate and ethylene glycol, manganese acetate as transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and a pigment having an average particle diameter of 0.3 μm were used.
m of titanium oxide particles was added to the polymer in an amount of 0.1% by weight and polymerized by a conventional method to obtain polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35 ° C) of 0.65. In addition to the polyethylene
10% by weight of 2,6-naphthalenedicarboxylate polymer pellets were mixed, dried at 170 ° C. for 3 hours, fed to another extruder hopper, and melted at a melting temperature of 300 ° C.
Average aperture of stainless steel fine wire with a wire diameter of 13 μm 24
The solution was filtered through a nonwoven-type filter of μm and led to the second or intermediate layer of the three-layer die.

Then, a three-layer laminated polymer in which the polymers led to the respective layers were laminated was passed through a slit die having an opening of 2 mm, and the surface was finished at 0.3 S and the surface temperature was 30.
It extruded on the rotating drum of ° C, and obtained the unstretched film. A line electrode to which a DC voltage of 6.5 KV was applied was brought close to the vicinity where the molten polymer was in contact with the cooling drum, and adhesion to the drum due to static electricity was promoted. Further, air cooled to about 10 ° C. was blown to the polymer on the drum to promote cooling on the air side. The unstretched film obtained in this way is
The film was stretched 3.0 times in the machine direction at ℃, then stretched 2.8 times in the transverse direction at 140 ° C., and further heat-set at 230 ° C. for 5 seconds, and the thickness of the polyethylene-2,6
-A biaxially oriented three-layer polyester film having a naphthalenedicarboxylate layer of 5 μm each was obtained. Table 1 shows the properties of the obtained biaxially oriented laminated polyester film.

[Example 2] Using a five-layer die, the first and fifth layers as the surface layers were polyethylene-2,6 in Example 1.
-Naphthalene dicarboxylate is derived, and the second and fourth layers, which are the surface portions of the intermediate layer, lead to a mixture of polyethylene terephthalate of Example 1 and polyethylene-2,6-naphthalenedicarboxylate in a weight ratio of 75:25. ,
The third layer, which is an intermediate layer excluding the intermediate layer surface portion, is derived from the polyethylene terephthalate of Example 1, and the thickness of each surface layer is 5 μm, and the thickness of each intermediate layer surface portion is 1
The same operation as in Example 1 was repeated, except that the thickness was changed to 2 μm and the total thickness of the laminated film to 250 μm. Table 1 shows the properties of the obtained biaxially oriented laminated polyester film.

[Examples 3 to 7] A biaxially oriented three-layer polyester film having a thickness of 250 µm was obtained in the same manner as in Example 1 except that the changes were as shown in Table 1. Table 1 shows the properties of the obtained biaxially oriented laminated polyester film.

Example 8 A biaxially oriented five-layer polyester film having a thickness of 250 μm was obtained in the same manner as in Example 2 except that the composition was changed as shown in Table 1. Table 1 shows the properties of the obtained biaxially oriented laminated polyester film.

Comparative Example 1 Polyethylene of Example 1
The same operation as in Example 1 was repeated except that the addition amount of the porous silica of 2,6-naphthalenedicarboxylate was changed to 1% by weight, and the polymer was converted into a single-layer film using a single-layer die. Table 1 shows the properties of the obtained biaxially oriented polyester film.

Comparative Example 2 The same operation as in Example 1 was repeated except that the polyethylene terephthalate of Example 1 was changed to a single-layer film using a single-layer die. Table 1 shows the properties of the obtained biaxially oriented polyester film.

Comparative Examples 3 to 5 A biaxially oriented three-layer polyester film having a thickness of 250 μm was obtained in the same manner as in Example 1 except that the conditions were changed as shown in Table 1. Table 1 shows the properties of the obtained biaxially oriented laminated polyester film.

[0061]

[Table 1]

In the above table, EN indicates an ethylene-2,6-naphthalate component.

[0063]

The biaxially oriented laminated polyester film of the present invention has the following excellent effects, and is particularly suitably used as an electrical insulating film for refrigerator motors. (1) It is excellent in heat deterioration resistance, and it is possible to reduce the size of electric equipment while maintaining high reliability. (2) A film excellent in delamination resistance and having little breakage at the time of slitting, layering at the time of loading a slot liner or wedge of a rotating machine, or layering at the time of peeling off an adhesive tape can be provided. (3) The amount of oligomers extracted is small and suitable for insulating motors for air conditioner refrigerators.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) H01B 3/42 H01B 3/42 F 5G333 17/56 17/56 A // B29K 67:00 B29K 67:00 105: 34 105: 34 B29L 7:00 B29L 7:00 9:00 9:00 F term (reference) 4F071 AA46 AB18 AF39 AH12 BA01 BB06 BC01 4F100 AA20 AA21B AA29 AK41 AK41A AK41B AK41C AK41J AK42B AL01 AL05B BA03 BA10BA BA DD07A DD07C DE01B EH20 EJ38 GB41 JG04 JJ03 JK06 JN01 YY00 YY00A YY00B YY00C 4F210 AA26 AB16 AG01 AG03 AH33 QC05 QC06 QG01 QG15 QG18 4J002 CF00 CF061 DE136 FA086 5G305 AB40 BA25 DA11 AB33

Claims (6)

[Claims] 1. A laminated film in which a layer (surface layer) composed of polyethylene-2,6-naphthalenedicarboxylate is laminated on both surfaces of a layer (intermediate layer) composed of polyethylene terephthalate. It contains a 2,6-naphthalenedicarboxylate component in an amount of 0.05% by weight or more and less than 15% by weight, and has a thickness of at least 1 μm
(The surface portion of the intermediate layer) contains an ethylene-2,6-naphthalenedicarboxylate component in an amount of 1% by weight or more and less than 30% by weight or more than 70% by weight and 99% by weight or less. A biaxially oriented laminated polyester film for electrical insulation, wherein the thickness is at least 2 μm or more, and the thickness of each surface layer is less than 10% based on the thickness of the laminated film. 2. The biaxially oriented laminated polyester film for electrical insulation according to claim 1, wherein the peel resistance between the intermediate layer and the surface layer of the laminated film is at least 10 as evaluated by JIS K5400-1990. 3. The biaxially oriented laminated polyester film for electrical insulation according to claim 1, wherein the surface center line average roughness (Ra) of at least one surface is in the range of 3 to 50 nm. 4. The biaxially oriented laminated polyester film for electrical insulation according to claim 1, which has a haze value of at least 20%. 5. The intermediate layer has an average particle size of 0.01 to 0.5 μm.
The biaxially oriented laminated polyester film for electrical insulation according to claim 4, comprising 0.1 to 1% by weight of titanium dioxide particles of m. 6. A polymer in a molten state mainly comprising polyethylene terephthalate, and polyethylene-2,6-
The biaxially oriented laminated polyester film for electrical insulation according to any one of claims 1 to 5, wherein the biaxially oriented polyester film is obtained by co-extruding a molten polymer mainly containing naphthalenedicarboxylate in a laminated state.