JPH0244087B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrical insulating sheet whose sheet-like base material is a film obtained from a versatile resin. This is what we provide. [Prior art] In electrical insulation systems, F class (JIS C4003
(Maximum allowable temperature 155℃ depending on the type of electrical equipment insulation)
Electrical insulation sheets used for class H (maximum temperature 180℃ according to JIS C4003 type of electrical equipment insulation), that is, electrical insulation sheets with heat resistance, include aromatic polyamide film, polyimide film, polyamide-imide film, and polyamide film. Examples include heat-resistant synthetic resin films such as arylate film, polysulfon film, polyether sulfon film, polyether ether ketone film, aromatic polyester film, and aromatic polyester imide film. On the other hand, silicone resin varnish containing at least fibrous potassium titanate and an inorganic filler can be used as a heat-resistant electrical insulating sheet that can be obtained at a low cost. It has been proposed that the wood be impregnated, dried, and hardened (patent application 1983-
No. 100654). [Problems to be Solved by the Invention] By the way, among the heat-resistant electrical insulating sheets, the former heat-resistant synthetic resin film itself is expensive and is not suitable as an electrical insulating sheet as an industrial material. , it is not satisfactory in terms of versatility. In addition, although electrical insulation sheets using the latter type of electrical insulation kraft paper or linter paper are generally satisfactory in terms of heat resistance, they have extremely poor dielectric breakdown voltage characteristics, and, for example, are usually insulated at 20 KV/mm or more. It has the disadvantage that it cannot be used as an electrical insulating sheet in fields that require breakdown voltage, such as rotating machines, generators, electromagnetic cookers, and coating materials for fire-resistant and heat-resistant electric wires. [Means for Solving the Problems] The electrical insulating sheet of the present invention comprises a sheet-like base material made of a thermoplastic resin film having a melting point of 200° C. or higher, and a silicone material cured on the sheet-like base material. It is composed of a resin layer,
Moreover, the silicone resin layer cured on the sheet-like base material is formed of a silicone resin varnish containing at least fibrous potassium titanate and an inorganic filler. In the electrical insulating sheet of the present invention having the above configuration, the sheet-like base material constituting the base is a thermoplastic resin film having a melting point of 200°C or higher, and is made of, for example, polyester (m .
p.: 248°C), e.g. polycarbonate obtained from bisphenol A and phosgene (mp: 222°C)
℃), a film made from a versatile resin such as triacetate (mp: 300℃), represented by the formula [-C ₆ H ₇ O ₂ (OCOCH ₃ ) ₃ ] _-o It is. The silicone resin varnish applied to the sheet-like base material made of a thermoplastic resin film having a melting point of 200° C. or higher contains at least fibrous potassium titanate and an inorganic filler, and this silicone resin varnish The silicone resin inside generally contains hydrogen atoms, vinyl groups,
For example, polydimethylsiloxane silicone resin, polydiphenylsiloxane silicone resin containing one or more substituents such as allyl group, aryl group, hydroxyl group, alkoxyl group having 1 to 4 carbon atoms, amino group, mercapto group, etc. Organopolysiloxane silicone resins such as polymethylphenylsiloxane silicone resins, epoxy-modified silicone resins modified with other resins, polyester-modified silicone resins, fatty acid-modified silicone resins, alkyd-modified silicone resins, and amino resin-modified silicone resins. Including,
One or two of various silicone resins such as polyacryloxyalkylalkoxysilane silicone resin and polyvinylsilane silicone resin.
Silicone resins obtained as a mixture of more than one species are used. In particular, among these various silicone resins, organopolysiloxane-based silicone resins contain 70% or more of the polysiloxane component in the silicone resin, and polyacryloxyalkylalkoxysilane-based silicone resins and polyvinylsilane-based silicone resins When the copolymerized ethylenically unsaturated monomer in the resin is used in an amount of 50% by weight or less, preferably 20% by weight or less, the electrical insulating sheet of the present invention has the characteristic that it has self-extinguishing properties. has. Furthermore, when an unmodified organopolysiloxane silicone resin is used, it has the characteristic of having excellent flexibility in addition to the above-mentioned self-extinguishing property. These silicone resins are provided in the form of solids, plastic pastes, liquids, or emulsions at room temperature, so silicone resin varnishes may be mixed with toluene, xylene,
Of course, it can be obtained by appropriately adding a solvent such as trichlene. The fibrous potassium titanate blended into the silicone resin varnish using the silicone resin imparts sufficient heat resistance and excellent surface strength to the electrical insulating sheet of the present invention. This fibrous potassium titanate has the general formula K ₂ O.
mTiO ₂・nH ₂ O (in the formula, m is a positive integer of 8 or less, n
represents a positive integer of 0 or 4 or less), and generally the fiber diameter is 0.1 to 0.7 μm and the fiber length is 10 to 50 μm.
These whiskers are produced using titanium oxide and potassium carbonate as raw materials by a calcination method, a hydrothermal method, a flux method, etc. The silicone resin varnish used in the present invention contains the above-mentioned fibrous potassium titanate. Although it can be used as it is, in order to achieve a better reinforcing effect, a silane coupling agent such as γ-aminopropyltriethoxysilane, γ- It is preferable to use fibers whose surfaces have been treated with a silane coupling agent such as glycidoxypropyltrimethoxysilane. The inorganic filler that is blended together with the fibrous potassium titanate in the silicone resin varnish has the effect of reinforcing the silicone resin layer formed by the silicone resin varnish, and includes, for example, aluminum hydroxide, antimony trioxide, Various inorganic materials such as titanium, mica, alumina, talc, glass fiber powder, rock wool fine fibers, silica powder, and clay are used. The silicone resin varnish used in the present invention contains the above-mentioned fibrous potassium titanate and an inorganic filler as essential ingredients, but if necessary, it may also contain, for example, a phosphate ester type or an organic halogen compound. Organic flame retardants such as mold, phosphazene compound type, crystal water releasing type such as calcined gypsum, alum, calcium carbonate, aluminum hydroxide, and hydrotalcite aluminum silicate, carbon dioxide gas releasing type, decomposition endothermic type, and phase transformation. Flame retardants such as endothermically decomposed inorganic compounds such as molds and inorganic flame retardants such as antimony compounds, metal carboxylates, organic tin compounds, titanium chelate compounds, tertiary amine compounds, peroxides, A curing agent such as a platinum-based catalyst, a curing accelerator, a coloring agent, etc. are added and contained. Note that the amount of fibrous potassium titanate and inorganic filler contained in the silicone resin varnish coated on a sheet-like base material made of a thermoplastic resin film having a melting point of 200°C or higher is determined by the amount of the fibrous potassium titanate and inorganic filler bonded by the silicone resin. The silicone resin is designed to achieve a balance between its action as an agent, the action of improving heat resistance and electrical insulation performance due to the fibrous potassium titanate, and the action of improving heat resistance and flame retardance due to the inorganic filler. About 1 to 200 parts by weight of fibrous potassium titanate per 100 parts by weight,
Preferably, about 4 to 200 parts by weight of inorganic filler is used. Further, the electrically insulating sheet of the present invention obtained using the sheet-like base material and the silicone resin varnish can be coated by dipping, spraying, roll coating, reverse roll coating, knife coating, or other coating methods. , the silicone resin varnish is applied to a sheet-like base material with a solid component adhesion amount of about 50 to 500 g/ ^m2 ,
The silicone resin in the silicone resin varnish is then dried and cured. Curing methods for curing silicone resin varnish applied to a sheet-like base material made of thermoplastic resin film include room temperature curing, heat curing, ultraviolet curing, and electron beam curing, but in the case of heat curing It is best to perform the treatment at about 150 to 200°C for about 1 to 30 minutes. [Example] Hereinafter, the specific structure of the electrical insulating sheet having both heat resistance and dielectric breakdown voltage resistance according to the present invention will be described using manufacturing examples. Example 1 Production of silicone resin varnish (1) Silicone resin [manufactured by Shin-Etsu Chemical Co., Ltd.: KR-
2706] 60 parts by weight (2) Titanium oxide 2.0 parts by weight (3) Zinc white 17.6 parts by weight (4) Mica [G-325] 23.5 parts by weight (5) Fibrous potassium titanate [Manufactured by Otsuka Chemical Co., Ltd.: Teismo D] 9.1 parts by weight (6) Xylene 26.5 parts by weight (7) Silicone resin curing agent [for KR-2706]
4.0 parts by weight The mixed composition consisting of the above (1) to (7) was stirred and mixed to obtain a silicone resin varnish consisting of a substantially uniform dispersion. The thickness of the obtained silicone resin varnish is
A coating amount of 145 g (solid content)/m ² was applied to a sheet-like base material [A] consisting of a 0.1 mm polyethylene terephthalate film [manufactured by Toray Industries, Inc.: Lumirror #100] using a dipping method, and then heated at 110°C. A drying process was carried out for 4 minutes at 180°C, followed by a curing process for 6 minutes at 180°C to obtain an electrically insulating sheet (a) which is an example product of the present invention. Example 2 The silicone resin varnish described in Example 1 above was applied to a sheet-like base material [B] made of a 0.10 mm thick polycarbonate film (Mitsubishi Gas Chemical Co., Ltd.: Iupilon Film) by a dipping method. amount
100g (solid content)/ ^m2 , and then dried under the same drying conditions as in Example 1,
An electrical insulating sheet (b) which is an example product of the present invention was obtained. Comparative Example The silicone resin varnish described in Example 1 was applied to electrically insulating kraft paper [Tomoekawa Paper Co., Ltd.]
Made by NT-190, thickness 0.30mm, weight 190g/m ² ], the amount of impregnation was 315g using the dipping method.
(solid content)/m ² and then dried at 110℃ for 4 minutes, followed by drying at 180℃ for 6 minutes.
A curing treatment was performed for 1 minute to obtain an electrical insulating sheet [C] for comparison. Electrical insulation sheets obtained in Examples 1 and 2 above
The physical property values of (a) and (b) were compared with those of the untreated film sheet-like base materials [A] and [B] and the electrical insulation sheet [C] obtained in the comparative example, and are shown in Table 1. .

〔effect〕

The electrical insulating sheet of the present invention is constructed as described above, and satisfies the requirements for electrical insulating sheets used for class F or class H in terms of heat resistance, and has high dielectric breakdown voltage. In terms of characteristics,
For example, sufficiently satisfies the dielectric breakdown voltage of at least 20 KV/mm or more required for electrical insulation sheets used in fields such as rotating machines, generators, electromagnetic cookers, and coating materials for fire-resistant and heat-resistant electric wires, that is, It can be used extremely effectively as an electrical insulating sheet that has both heat resistance and dielectric breakdown voltage resistance. Further, the electrical insulating sheet of the present invention is composed of a thermoplastic resin film made of a general-purpose resin, that is, a resin that is inexpensively supplied, and a silicone resin layer containing at least fibrous potassium titanate and an inorganic filler. Since it is a film made of a heat-resistant synthetic resin, it does not have the risk of being expensive, and has the advantage that it can be manufactured at a low cost.

Claims (1)

[Claims] 1. A silicone resin varnish containing at least fibrous potassium titanate and an inorganic filler is applied to a sheet-like base material made of a thermoplastic resin film having a melting point of 200°C or higher, and dried. An electrical insulating sheet having both heat resistance and dielectric breakdown voltage resistance, characterized by being hardened. 2. Heat resistance and dielectric breakdown voltage characteristics according to claim 1, wherein the silicone resin varnish containing at least fibrous potassium titanate and an inorganic filler is a silicone resin varnish containing an inorganic or organic flame retardant. An electrical insulation sheet that combines