JP2007130898A - Heat-resistant insulation paper and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inexpensive insulation paper which has excellent heat-resistant insulation, smoothness, water resistance and resistance to insulation oils and is used in electric cars, transformers for high-voltage power transmission, etc. <P>SOLUTION: The heat-resistant insulation paper consists of two or more layers, and at least one outer layer is a polyamideimide resin layer of a glass transition temperature of ≥200°C. Preferably, the layers other than the polyamideimide resin layer of a glass transition temperature of ≥200°C are films and/or nonwoven fabrics composed of at least one of polyethylene terephthalate, polyethylene naphthalate, aromatic polyamides, aromatic polyimides and polyamideimides other than the above polyamideimides. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel heat-resistant insulating paper. More specifically, the present invention relates to a heat-resistant insulating paper having a multilayer structure using a heat-resistant polyamide-imide resin as an outer layer, showing excellent electrical insulation even at high temperatures, and having excellent water resistance and surface smoothness.

Conventionally, aramid nonwoven fabrics such as cellulose and aromatic polyamide, polyethylene terephthalate, polyethylene naphthalate film, and the like have been used for insulating paper. In particular, aramid nonwoven fabrics and polyethylene naphthalate films have been used for heat resistant applications. However, aramid nonwoven fabrics may have insufficient heat resistance in terms of water absorption and surface smoothness. As these improvements, a material in which an aramid nonwoven fabric is bonded to the front and back of a polyethylene terephthalate film or a polyethylene naphthalate film seems to be commercially available, but water absorption and surface smoothness are not improved. In addition, composite insulating paper has been proposed in which an insulating material such as polyethylene terephthalate is laminated on a plastic substrate reinforced with inorganic or organic fibers, but the essential heat resistance has not been improved, and there are concerns about problems such as curling. (See, for example, Patent Document 1). Further, a nonwoven fabric made of polyimide fibers has been studied. However, the nonwoven fabric system has a problem that thickness unevenness and surface smoothness are poor and the price is high. (See, for example, Patent Document 2) In particular, in the insulating paper used for high-voltage power transmission, fluff and thick spots on the surface may cause local dielectric breakdown.
An object of the present invention is to provide a water- and heat-resistant electrical insulating paper at low cost, which can be applied to high voltage applications and has a smooth surface with less fluff.

JP 2004-146093 A Japanese Patent Laid-Open No. 2003-96698

  The present invention provides an inexpensive electrical insulating paper that is excellent in heat resistance insulation, smoothness, water resistance, and insulation oil resistance, and that is used in electric vehicles, transformers for high-voltage power transmission, and the like.

  As a result of intensive studies in view of the above problems, the present inventors have reached the present invention. That is, this invention relates to the following heat-resistant insulating paper and its manufacturing method.

(1) A heat-resistant insulating paper, which is an insulating paper formed from a plurality of layers, wherein at least one outer layer is a polyamide-imide resin layer having a glass transition temperature of 200 ° C. or higher.

(2) After applying or impregnating a polyamideimide resin solution having a glass transition temperature of 200 ° C. or higher on one or both sides of a film or nonwoven fabric made of polyethylene terephthalate, polyethylene naphthalate, aromatic polyamide, aromatic polyimide and polyamideimide, A method for producing a heat-resistant insulating paper characterized by drying.

  The present invention provides an insulating paper excellent in heat insulation, mechanical strength, water resistance, insulation oil resistance, and surface smoothness by using a polyamideimide resin having a glass transition temperature of 200 ° C. or more as an outer layer to form a multilayer structure. provide. The heat-resistant insulating paper of the present invention can provide insulating paper such as automobiles and high-voltage power transmission transformers.

A major feature of the present invention is that a heat-resistant polyamide-imide resin layer is formed on one side or both sides of conventionally used insulating paper.
In this case, it is important that the polyamide-imide resin has high heat resistance, and as a guide, the glass transition temperature is 200 ° C. or higher, preferably 250 ° C. or higher. This is because when the glass transition temperature is 200 ° C. or lower, the resin deteriorates due to heat shrinkage or dimensional change when used at a high temperature for a long time, and mechanical strength and insulating properties are lowered. The upper limit of the glass transition temperature is not particularly limited, but is preferably 400 ° C. or lower from the viewpoint of varnish production stability and the like.

  Generally, a polyamideimide resin is synthesized from trimellitic anhydride and diisocyanate or trimellitic chloride and diamine by heating and stirring in an aprotic polar solvent. In this case, a method of synthesizing from trimellitic anhydride and diisocyanate is advantageous from the viewpoint of ease of polymerization and cost. In the present specification, the amine component is described as the corresponding diisocyanate component, but it should be understood that the diisocyanate compound includes the corresponding diamine compound.

  Examples of the acid component used in the production of the polyamideimide resin having a glass transition temperature of 200 ° C. or higher used in the present invention include pyromellitic acid, 3,3 ′, 4,4 ′ in addition to the above trimellitic acid and its anhydride. -Biphenyltetracarboxylic acid, 3,3 ', 4,4'-biphenylsulfonetetracarboxylic acid, 3,3', 4,4'-benzophenone tetracarboxylic acid, 3,3 ', 4,4'-biphenyl ether tetra Tetracarboxylic acids such as carboxylic acid, ethylene glycol bisanhydro trimellitate, propylene glycol bisanhydro trimellitate and their anhydrides, oxalic acid, adipic acid, malonic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid, Dicarboxypolybutadiene, dicarboxypoly (acrylonitrile-butadiene), dicar Aliphatic dicarboxylic acids such as xypoly (styrene-butadiene), 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 4,4′-dicyclohexylmethanedicarboxylic acid, alicyclic dicarboxylic acids such as dimer acid, terephthalic Examples include aromatic dicarboxylic acids such as acid, isophthalic acid, diphenylsulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, and naphthalenedicarboxylic acid. Among these, trimellitic anhydride is most preferable in terms of reactivity, heat resistance, solubility, and the like. Dimensional stability is obtained by changing a part of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. To preferred. When 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride or 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is used, the amount of copolymerization is 100 mol of the acid component. % Is preferably 5 to 40 mol%. If the copolymerization amount is 5 mol% or less, the effect of copolymerization is not sufficiently exhibited, and if it is 40 mol% or more, it is difficult to dissolve in a polymerization solvent such as N-methyl-2-pyrrolidone or N, N′-dimethylacetamide. is there.

  Examples of the diisocyanate used in the production of the polyamideimide resin having a glass transition temperature of 200 ° C. or higher used in the present invention include aliphatic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and alicyclic groups such as 4,4′-dicyclohexylmethane diisocyanate. Diisocyanate, 4,4′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate, 3,3′-dimethyl-4,4′-diisocyanate diphenyl, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene Examples include aromatic diisocyanates such as range diisocyanate, 1,5-naphthalene diisocyanate, and 1,8-naphthalene diisocyanate. Among these, heat resistance, mechanical properties, dissolution 4,4'-diphenylmethane diisocyanate and the like, 2,4-tolylene diisocyanate, 3,3'-dimethyl-4,4'-diisocyanate diphenyl, 1,5-naphthalene diisocyanate, isophorone diisocyanate and the like are preferable. In particular, 3,3'-dimethyl-4,4'-diisocyanate diphenyl and 1,5-naphthalene diisocyanate are preferable from the viewpoint of dimensional stability. These components are each preferably copolymerized in an amount of 20 mol% or more, more preferably 40 mol% or more when the total diamine component is 100 mol%. The upper limit may be 100 mol%.

Polyamideimide resin having a glass transition temperature of 200 ° C. or higher used in the present invention is 60 in a polar solvent such as N, N′-dimethylacetamide, N-methyl-2-pyrrolidone, N, N′-dimethylformamide, γ-butyrolactone, and the like. It can be easily produced by stirring while heating to ~ 200 ° C. The molecular weight of the polyamideimide resin is 0.3 dl / g or more in logarithmic viscosity, preferably 0.5 dl / g or more, more preferably 0.7 dl / g or more. When the logarithmic viscosity is 0.3 dl / g or less, the polyamide-imide resin coating film becomes brittle, and the heat resistance and mechanical strength during use at high temperature and for a long period of time decrease. The upper limit of the logarithmic viscosity is not particularly limited, but is preferably 2.0 dl / g or less from the viewpoint of workability. These logarithmic viscosities can be controlled by adjusting the charged molar ratio of the acid component and the diisocyanate component, and the range of the acid component / diisocyanate component is preferably 0.7 to 1.2.
In this case, an organic amine compound such as triethylamine, diethylenetriamine, or diazabicycloundecene, or a metal compound such as potassium fluoride, sodium fluoride, cesium fluoride, or sodium methoxide can be used as a catalyst as necessary.

The heat-resistant insulating paper of the present invention is a composite insulating paper of a polyamideimide resin having a glass transition temperature of 200 ° C. or higher and an insulating paper that has been used conventionally. This is because by making it composite, the polyamideimide layer can be thinned, and the heat resistance, electrical insulation, moisture resistance, and mechanical strength peculiar to polyamideimide can be sufficiently exhibited, and it can be manufactured at low cost.
The conventional insulating paper that can be used in the present invention does not need to have particularly high heat resistance, and films and nonwoven fabrics such as polyethylene terephthalate and polyethylene naphthalate, cellulose nonwoven fabrics, aromatic polyamide and aromatic polyimide films and nonwoven fabrics are used. It is done. Among these, a film is preferable to a non-woven fabric because of smoothness and fluff, and polyethylene naphthalate is particularly preferable from the viewpoint of price and workability. Therefore, in the present invention, the insulating paper does not necessarily require a paper layer, and may be a composite film used for the purpose of electrical insulation.

  The layer structure of the composite heat-resistant insulating paper of the present invention is not particularly limited except that the outer layer is provided with a polyamideimide resin layer having a glass transition temperature of 200 ° C. or higher, and may be two or more layers. However, a three-layer structure in which both outer layers are made of polyamideimide is preferable in order to fully exhibit the properties of polyamideimide. In this case, the thickness of the polyamideimide resin layer having a glass transition temperature of 200 ° C. or higher is 3 to 100 μm, preferably 5 to 50 μm. If the thickness of the polyamideimide resin layer is 3 μm or less, the properties of the polyamideimide resin may not be exhibited, and if it is 100 μm or more, the coating and drying workability may be deteriorated.

Although there is no restriction | limiting in manufacture of the composite heat resistant insulating paper of this invention, The following method is mentioned.
(1) A film of polyamideimide having a glass transition temperature of 200 ° C. or more and a film or non-woven fabric of conventional insulating paper are bonded via an adhesive or directly by thermocompression bonding.
(2) A polyamideimide resin solution having a glass transition temperature of 200 ° C. or higher is applied to or impregnated on a film or nonwoven fabric of insulating paper, and then dried.
Among these, the method (2) is preferable from the viewpoint of ease of processing and cost.
In this case, the polyamide-imide resin solution having a glass transition temperature of 200 ° C. or higher has a colorant, a dispersant, an inorganic filler, a leveling agent, an antifoaming agent, polyester, polyamide, polyimide, Other resins such as polyurethane, silicone release agents, crosslinking agents, and the like can be blended. Examples of the crosslinking agent include bifunctional or higher functional epoxy resins, melamine resins, and isocyanate compounds.

  The insulating paper of the present invention can be used for applications such as capacitors, cables, coils, and transformers. Therefore, by using the heat-resistant insulating paper of the present invention, it is possible to produce a capacitor, cable, coil, and transformer excellent in high-temperature insulating properties, mechanical strength, water resistance, and insulating oil resistance.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. In addition, the measured value in an Example is a value measured with the following method.
1. Logarithmic viscosity A solution prepared by dissolving 0.5 g of a polymer in 100 ml of NMP (N-methyl-2-pyrrolidone) was measured at 25 ° C. using an Ubbelohde viscosity tube.
2. Heat resistance A sample of 4 cm square was sandwiched between two 5 cm square glass plates, and after fixing the 4 sides with clips, the area shrinkage after standing in an oven at 200 ° C. for 1 hour was measured and Judged by criteria.
○: Shrinkage is 5% or less ×: Shrinkage is 5% or more Dielectric breakdown voltage Measured according to the method described in ASTM D149.
The breakdown voltage when a voltage of 60 Hz was applied at a rate of 0.5 kV / sec in the thickness direction of the test piece in oil was read. The unit is kV.
4). Surface smoothness The surface of the insulating paper was visually observed for surface irregularities and fluff states, and judged according to the following criteria.
○: The surface is smooth and no fluff is seen.
Δ: Unevenness is seen on the surface, but no fluff is seen.
X: Many fluff is seen.
5. Water absorption rate Each sample of insulating paper 5 cm × 5 cm is immersed in ion exchange water at 25 ° C. for 24 hours, and after sufficiently wiping off water droplets on the surface, it is precisely weighed with an electronic balance. (W1) Next, the same sample is dried in a hot air dryer at 120 ° C. for 1 hour, left in a dry desiccator for 30 minutes or more, and then weighed again. (W0) The water absorption was determined by the following equation.
Water absorption (%) = 100 × (W1-W0) / W1
The unit is%.
6). Glass transition temperature Polyamideimide resin solution was applied on a 100 μm polyester film so that the film thickness was about 30 μm, dried at 100 ° C. for 10 minutes, then peeled off from the polyester film, fixed to a metal frame, and further 1 at 250 ° C. The inflection point of the loss elastic modulus measured for the time-dried film using a dynamic viscoelasticity measuring device manufactured by IT Measurement & Control Co., Ltd. under the conditions of a heating rate of 5 ° C./min and a frequency of 110 Hz was defined as the glass transition temperature.
The unit is ° C.

(Synthesis of polyamideimide resin A)
Trimellitic anhydride (TMA) 0.98 mol and diphenylmethane 4,4′-diisocyanate (MDI) 1 mol in a four-necked flask equipped with a cooling tube and a nitrogen gas inlet so that the solid content concentration becomes 20% The mixture was charged with N-methyl-2-pyrrolidone (NMP), heated to 120 ° C. with stirring and allowed to react for about 3 hours. This polyamideimide resin had a logarithmic viscosity of 0.65 dl / g and a glass transition temperature of 280 ° C.

(Synthesis of polyamideimide resin B)
Using the same apparatus as in Example 1, 0.99 mol of TMA, 0.8 mol of 3,3′-dimethyl-4,4′-diisocyanate biphenyl (TODI), 0.24 of 2,4-tolylene diisocyanate (TDI) Mole was charged together with NMP so that the solid content concentration was 20%, and reacted at 90 ° C. for about 1 hour with stirring. The obtained polyamideimide resin had a logarithmic viscosity of 0.86 dl / g and a glass transition temperature of 310 ° C.

(Synthesis of polyamideimide resin C)
In a four-necked flask equipped with a condenser and a nitrogen gas inlet, 0.85 mol of TMA, 0.15 mol of benzophenonetetracarboxylic anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride 1 mol, 1 mol of TODI, and 0.01 mol of diazabicycloundecene were charged together with NMP so that the solid concentration would be 15%, and the temperature was raised to 80 ° C. with stirring and reacted for about 2 hours. The obtained polyamideimide resin had a logarithmic viscosity of 0.78 dl / g and a glass transition temperature of 330 ° C.

(Synthesis of polyamideimide resin D)
In a four-necked flask equipped with a condenser and a nitrogen inlet, 0.7 mol of TMA, 0.30 mol of benzophenonetetracarboxylic anhydride, 1 mol of 1,5-naphthalenediocyanate and 0.01 mol of diazabicycloundecene were solidified. The mixture was charged with N-methyl-2-pyrrolidone so as to have a partial concentration of 15% and reacted at 80 ° C. for about 2 hours. The obtained polyamideimide resin had a logarithmic viscosity of 0.85 dl / g and a glass transition temperature of 375 ° C.

(Synthesis of polyamideimide resin E)
TMA 0.6 mol, benzophenone tetracarboxylic anhydride 0.3 mol, biphenyl tetracarboxylic anhydride 0.1 mol, 1,5-naphthalene diisocyanate 0.9 in a four-necked flask equipped with a condenser and a nitrogen inlet Mole, 0.1 mol of tolylene diisocyanate, and 0.01 mol of diazabicycloundecene were charged together with N-methyl-2-pyrrolidone so that the solid concentration was 15%, and reacted at 80 ° C. for about 2 hours. The logarithmic viscosity of this polyamideimide resin was 0.88 dl / g, and the glass transition temperature was 367 ° C.

(Examples of heat-resistant insulating paper-1, 2, 3, 4, 5)
Each of the polyamideimide resins A, B, C, D, and E synthesized above was applied on one side of a polyethylene naphthalate film (188 μm manufactured by Teijin) so that the film thickness was 10 μm, and then dried at 100 ° C. for 10 minutes. Furthermore, the film was coated on the back surface so that the film thickness was 10 μm, dried at 100 ° C. for 10 minutes, and then heat-treated at 150 ° C. for 30 minutes. Table 1 shows the characteristics of the obtained heat-resistant insulating papers.

(Example 6 of heat-resistant insulating paper)
Using the polyamideimide resin A, the base material was a polyethylene terephthalate film (188 μm manufactured by Toyobo Co., Ltd.), and coating, drying, and heat treatment were performed under the same conditions as in Production Example 1 of heat-resistant insulating paper. Table 1 shows the characteristics of the obtained heat-resistant insulating paper.

(Example 7 of heat-resistant insulating paper)
The polyamide-imide resin A solution is impregnated with an aramid nonwoven fabric (Nomex: 5 mil), squeezed with a squeeze roll to adhere 100 g / m ² , dried at 100 ° C. for 10 minutes, and then crimped with a 150 ° C. calender roll, and further at 200 ° C. Dry for 30 minutes. Table 1 shows the characteristics of the obtained heat-resistant insulating paper.

(Comparative Examples-1, 2, 3)
Table 1 shows the characteristics of the polyethylene terephthalate film, the polyethylene naphthalate film, and the aramid nonwoven fabric that are not coated or impregnated with the polyamideimide resin.

表中の略号は以下の通りである。
ＰＡＩ：ポリアミドイミド
ＰＥＴ：ポリエチレンテレフタレート
ＰＥＮ：ポリエチレンナフタレート (Comparative Example 4)
A composite insulating paper was prepared in the same manner as in Example 1 using Viromax HR85ET (Toyobo's polyamideimide resin solution: glass transition temperature 85 ° C.). Table 1 shows the characteristics of the obtained insulating paper.

Abbreviations in the table are as follows.
PAI: Polyamideimide PET: Polyethylene terephthalate PEN: Polyethylene naphthalate

  The present invention relates to a heat-resistant insulating paper excellent in high-temperature insulation, mechanical strength, water resistance, and insulation oil resistance by using a polyamideimide resin layer having a glass transition temperature of 200 ° C. or more as an outer layer. It is possible to provide a heat-resistant insulating paper useful for.

Claims (6)

  A heat-resistant insulating paper, which is an insulating paper formed of a plurality of layers, wherein at least one outer layer is a polyamide-imide resin layer having a glass transition temperature of 200 ° C or higher.   Other than the polyamide-imide resin layer having a glass transition temperature of 200 ° C. or higher, at least one film or nonwoven fabric selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, aromatic polyamide, aromatic polyimide, and polyamideimide other than the above polyamideimide The heat-resistant insulating paper according to claim 1, wherein the heat-resistant insulating paper is provided.   A heat-resistant insulating paper having a three-layer structure in which a polyamideimide resin layer having a glass transition temperature of 200 ° C. or higher is formed on both surfaces of a polyethylene naphthalate film.   The polyamide-imide resin having a glass transition temperature of 200 ° C. or higher contains 3,3′-dimethyl-4,4′-diisocyanate biphenyl and / or 1,5-naphthalene diisocyanate as a diisocyanate component. The heat-resistant insulating paper according to any one of 3 above.   Polyamideimide resin having a glass transition temperature of 200 ° C. or higher is 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and / or 3,3 ′, 4,4′-biphenyltetracarboxylic acid as an acid component. The heat-resistant insulating paper according to any one of claims 1 to 4, comprising a dianhydride.   Apply or impregnate a polyamideimide resin solution having a glass transition temperature of 200 ° C. or higher on one or both sides of a film or nonwoven fabric made of polyethylene terephthalate, polyethylene naphthalate, aromatic polyamide, aromatic polyimide and polyamideimide, and then dry. A method for producing heat-resistant insulating paper characterized by the above.