JPS6352405B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a heat-resistant electrical insulating sheet that uses kraft paper or linter paper for electrical insulation as a sheet-like base material, and has flame retardancy, heat resistance, electrical insulation performance, etc. obtained from wholly aromatic polyamide fibers. The purpose of the present invention is to provide an electrically insulating sheet that has substantially the same performance as the nonwoven fabric produced by the present invention and can be obtained at an extremely low cost. For example, as insulation sheets for various heavy electrical machinery,
It is known that nonwoven fabrics made from wholly aromatic polyamide fibers are suitable for having excellent properties such as flame retardancy, heat resistance, and electrical insulation performance. Because fully aromatic polyamide fiber itself is expensive,
The reality is that the price of nonwoven fabrics is rapidly increasing, and their versatility is not satisfactory. The present invention provides an electrically insulating sheet in which a silicone resin varnish containing at least fibrous potassium titanate and an inorganic filler is impregnated into a sheet-like base material made of electrically insulating kraft paper or linter paper, dried, and cured. By doing so, it was possible to provide a sheet that has excellent flame retardancy and heat resistance in addition to high electrical insulation performance, and can be obtained at a low cost. Hereinafter, the constituent components of the heat-resistant electrical insulating sheet of the present invention will be explained. (1) Sheet-like base material The sheet-like base material constituting the base of the heat-resistant electrical insulating sheet of the present invention is kraft paper or linter paper for electrical insulation, and generally has a thickness of 4
~15 mils are used. When the electrical properties of the obtained electrical insulating sheet are important, kraft paper or linter paper with a small thickness and low density is used, and when the mechanical properties are important, mechanical strength However, kraft paper is generally used when mechanical strength is required, and linter paper is used when electrical properties are particularly required, or when electrical properties are required as well as machinability and punchability. Used when punchability is required. (2) Fibrous potassium titanate Fibrous potassium titanate is blended into the silicone resin varnish that is impregnated into the aforementioned sheet-like base material made of kraft paper or linter paper.
This introduces sufficient heat resistance and excellent surface strength into the sheet of the present invention. Fibrous potassium titanate has the following general formula:
It is expressed as K ₂ O・mTiO ₂・nH ₂ O (in the formula, m is a positive integer of 8 or less, n is 0 or a positive integer of 4 or less), and generally has a fiber diameter of 0.1 to 0.7 μm and a fiber length of 10
It is a whisker of ~50 μm and is manufactured using titanium oxide and potassium carbonate as raw materials by a calcination method, a hydrothermal method, a flux method, etc. In the present invention, the aforementioned fibrous potassium titanate can be used as it is in the silicone resin varnish, but in order to achieve a better reinforcing effect, 0.05 to 1.0% by weight of the fibrous potassium titanate is added. degree of silane coupling agent,
For example, γ-aminopropyltriethoxysilane,
It is preferable to use fibers whose surfaces have been treated with a silane coupling agent such as γ-glycidoxypropyltrimethoxysilane. (3) Inorganic filler The inorganic filler is mixed into a silicone resin varnish in the same way as the fibrous potassium titanate mentioned above, impregnated into a sheet-like base material made of kraft paper or linter paper, and dried and hardened. It serves to reinforce the synthetic resin layer with silicone resin formed by, for example, aluminum hydroxide, antimony trioxide, titanium oxide, mica, alumina, talc, glass fiber powder, rock wool fine fiber, silica powder, Various inorganic materials such as clay are used. (4) Flame retardant Claim 2 which is an embodiment of the present invention
In the invention in item 1 and the invention in item 4, an electrical insulating sheet having superior flame retardant properties in addition to heat resistance is obtained, and the flame retardant used here is not particularly limited, but For example, organic flame retardants such as phosphate ester type, organic halogen compound type, phosphazene compound type, crystal water releasing type such as calcined gypsum, alum, calcium carbonate, aluminum hydroxide, hydrotalcite aluminum silicate, carbon dioxide gas There are endothermic decomposition type inorganic compounds such as release type, decomposition endothermic type and phase change type inorganic compounds, and inorganic flame retardants such as antimony compounds. (5) Silicone resin varnish The silicone resin varnish used in the heat-resistant electrical insulating sheet of the present invention is made of fibrous potassium titanate as explained in section (2) above, and inorganic potassium titanate as explained in section (3) above. It contains a filler as an essential component, and if necessary, the flame retardant etc. explained in the above item (4), such as metal carboxylate, organic tin compound, titanium chelate compound, tertiary amine compound. , a curing agent or curing accelerator such as a peroxide, a platinum-based catalyst, a coloring agent, etc. are used. The silicone resin varnish used in the present invention is one in which the silicone resin in the varnish provides the sheet of the present invention with sufficient heat resistance and electrical insulation performance, and generally contains hydrogen atoms, vinyl groups, allyl groups. , aryl group, hydroxyl group,
For example, polydimethylsiloxane-based silicone resin, polydiphenylsiloxane-based silicone resin, polymethylphenylsiloxane-based silicone resin and Epoxy-modified silicone resins modified with other resins, polyester-modified silicone resins,
One type of silicone resin, including organopolysiloxane silicone resins such as fatty acid-modified silicone resin, alkyd-modified silicone resin, and amino resin-modified silicone resin, as well as polyacryloxyalkylalkoxysilane-based silicone resin and polyvinylsilane-based silicone resin. Alternatively, a silicone resin varnish obtained as a mixture of two or more types is used. As mentioned above, in the present invention, one or a mixture of two or more of various silicone resins such as organopolysiloxane silicone resin, polyacryloxyalkylalkoxysilane silicone resin, and polyvinylsilane silicone resin may be optionally used in combination. Silicone resin varnish obtained by In the polyvinylsilane silicone resin, the amount of copolymerized ethylenically unsaturated monomer used is 50% by weight or less, preferably 20% by weight or less.
This is preferable in that the resulting heat-resistant electrical insulating sheet of the present invention also has self-extinguishing properties. In addition, especially when a silicone resin varnish made of an unmodified organopolysiloxane silicone resin is used, the electrical insulating sheet of the present invention has the property of having excellent flexibility as well as self-extinguishing properties. Express. 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. (6) Melamine resin, phenolic resin Melamine resin and phenolic resin are used in the third and fourth inventions that are embodiments of the present invention, and are excellent in the electrical insulating sheet of the present invention. The purpose of the present invention is to provide a sheet with excellent water resistance, particularly a slight decrease in electrical resistance after moisture absorption, and excellent mechanical strength, especially mechanical strength when wet. The heat-resistant electrical insulating sheet of the present invention is as described above.
(1), (2), (3), and (5) as essential components, and is a silicone resin varnish that is impregnated into a sheet-like base material made of kraft paper or linter paper. The amount of fibrous potassium titanate and inorganic filler to be contained is determined by the effect of the silicone resin as a binder, the effect of the fibrous potassium titanate to improve heat resistance and electrical insulation performance, and the effect of the inorganic filler. In order to achieve a well-balanced effect of improving heat resistance and flame retardancy, about 1 to 200 parts by weight of fibrous potassium titanate and about 4 to 200 parts by weight of inorganic filler are added to 100 parts by weight of silicone resin. Preferably, those containing The sheet-like base material made of the above-mentioned kraft paper or linter paper is coated with solid components in an amount of about 50 to 500 g/m ² by impregnation methods such as dipping, spraying, roll coating, reverse roll coating, and knife coating. is impregnated with the silicone resin varnish, and then the silicone resin in the silicone resin varnish is dried and cured to obtain the heat-resistant electrical insulating sheet of the present invention. Methods for curing the silicone resin varnish impregnated into a sheet-like base material made of kraft paper or linter paper 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. Hereinafter, the specific structure of the heat-resistant electrically insulating sheet of the present invention will be explained using manufacturing examples, and the physical properties of the obtained sheet will also be explained. Example 1 Production of silicone resin varnish (1) Silicone resin 60 parts by weight [manufactured by Shin-Etsu Chemical Co., Ltd.: KR-2706] (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 9.1 parts by weight [manufactured by Otsuka Chemical Co., Ltd.: Teismo D] (6) Xylene 26.5 parts by weight (7) Silicone resin curing agent 4.0 parts by weight [KR-2706 ] The mixed composition consisting of (1) to (7) above was stirred and mixed to obtain a silicone resin varnish [A] consisting of a substantially uniform dispersion. The obtained silicone resin varnish [A],
Kraft paper for electrical insulation [manufactured by Tomoekawa Paper Co., Ltd.: NT-
190, thickness 0.30 mm, mass 190 g/m ² ] was impregnated with an impregnation amount of 315 g (solid content)/m ² by the dipping method, and then dried at 110°C for 4 minutes. This was followed by a curing treatment at 180° C. for 6 minutes to obtain an electrically insulating sheet (a) which is an example of the present invention. Comparative Example 1 A mixed composition (i.e., fibrous A mixture composition containing no potassium titanate) was stirred and mixed to obtain a silicone resin varnish from a substantially uniform dispersion. Subsequently, the silicone resin varnish [I] was impregnated into a sheet-like base material made of the same electrically insulating kraft paper used in Example 1 to an impregnation amount of 315 g (solid content)/m ² by a dipping method. Then, drying was performed under the same drying conditions as in Example 1 to obtain an electrical insulating sheet (a) for comparison. Comparative Example 2 A mixed composition consisting of (1) and (5) to (7) in the "Production of silicone resin varnish" section in Example 1 (i.e., a mixed composition containing no inorganic filler) was stirred. were mixed to obtain a silicone resin varnish consisting of a substantially uniform dispersion. Subsequently, the silicone resin varnish was impregnated into a sheet-like base material made of the same electrically insulating kraft paper used in Example 1 to an impregnation amount of 315 g (solid content)/m ² by a dipping method. Then, drying was performed under the same drying conditions as in Example 1 to obtain an electrical insulating sheet (b) for comparison. Comparative Example 3 A mixed composition consisting of (1), (6), and (7) in the section "Production of silicone resin varnish" in Example 1 (i.e., containing fibrous potassium titanate and an inorganic filler) A silicone resin varnish is obtained by stirring and mixing a substantially uniform dispersion liquid (not a mixed composition).
I got it. Subsequently, the silicone resin varnish was impregnated into a sheet-like base material made of the same electrically insulating kraft paper used in Example 1 to an impregnation amount of 315 g (solid content)/m ² by a dipping method. Then, drying was performed under the same drying conditions as in Example 1 to obtain an electrical insulating sheet (c) for comparison. Example 2 The silicone resin varnish [A] described in Example 1 was applied to electrically insulating kraft paper [manufactured by Sanyo Kokusaku Pulp Co., Ltd.: FL-135, thickness 0.25 mm, weight
A sheet-like base material consisting of 135 g/m ² ] was impregnated with an impregnation amount of 355 g (solid content)/m ² by a dipping method, and then dried under the same drying conditions as in Example 1. Electrical insulation sheet as an example product
I got (b). Example 3 The silicone resin varnish [A] explained in Example 1 was coated with electrically insulating linter paper [thickness:
0.30 mm, mass 135 g/m ² ] was impregnated with an impregnation amount of 320 g/m ² by a dipping method, and then dried under the same drying conditions as in Example 1 to obtain the An electrical insulating sheet (c) as an example product was obtained. Example 4 The silicone resin varnish [A] described in Example 1 was applied to electrically insulating kraft paper [manufactured by Sanyo Kokusaku Pulp Co., Ltd.: FL-135, thickness 0.25 mm, weight
135g/m ² ] with melamine resin [Nippon Carbide Co., Ltd.]
A sheet-like base material made of kraft paper with a resin adhesion of 5% by weight obtained by treatment with a 5% by weight aqueous solution of [S-260] was impregnated with an impregnation amount of 385g/m ² by a dipping method, and then Drying was carried out under the same drying conditions as in Example 1 to obtain an electrical insulating sheet (d) which is an example product of the present invention. Tables 1 and 2 show various physical property values of the electrically insulating sheets obtained in the above Examples and Comparative Examples and the electrically insulating kraft paper used as the sheet-like base material in Example 1. In addition, the thickness and mass of the physical property values shown in Tables 1 and 2 are the values measured in accordance with JIS C-2111, the oxygen index is the value measured in accordance with JIS K-7201, and the insulation resistance is the value measured in accordance with JIS K-7201. Values measured in accordance with JIS K-6911, heat shrinkage rates are values obtained by placing each sample in a hot air circulation dryer at 180℃ and measuring the dimensional change rate (shrinkage rate) after 24 hours, withstand voltage is JIS C 2111
These are the values measured in accordance with the electrical insulating paper test method.

【table】

【table】

[Table] The heat-resistant electrical insulating sheet of the present invention has a structure as detailed above, that is, a sheet-like base material made of kraft paper or linter paper for electrical insulation is filled with at least fibrous potassium titanate and an inorganic material. It is composed of a silicone resin varnish that has been impregnated, dried, and hardened, and can be used extremely effectively as a sheet that exhibits excellent electrical insulation properties in addition to excellent heat resistance. be.

Claims (1)

[Claims] 1. A sheet-like base material made of kraft paper or linter paper for electrical insulation is impregnated with a silicone resin varnish containing at least fibrous potassium titanate and an inorganic filler, dried and hardened. An electrical insulating sheet with heat resistance. 2. The heat-resistant electrical insulating sheet 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. 3. The heat resistance according to claim 1 or 2, wherein the sheet-like base material made of kraft paper or linter paper for electrical insulation is a sheet-like base material treated with melamine resin or phenol resin. Electric insulation sheet with. 4. The sheet-like base material treated with a melamine resin or a phenolic resin is a sheet-like base material treated with a melamine resin or a phenolic resin containing an inorganic or organic flame retardant. Electrical insulation sheet with heat resistance.