JPH0227608A - Heatproof insulating compound sheet - Google Patents

Abstract

PURPOSE:To have a raise in the heatproof limit of the sheet in the title, by using polyorganosiliceus-quioxane prepared through a heat curing process on an organosiliceus-quioligomer as a binder of scaly or fibrous power which has a specific aspect ratio. CONSTITUTION:As a reinforcing filler, it is required to prepare a composition consisting of 10 to 1,000wt.% of scaly or fibrous powder having its aspect ratio of not less than 10 against 100wt.% of polyorganosiliceus-quioxane. The reinforcing filler has a function to form the skeletal structure of a compound sheet so as to produce a reinforcing effect. This function therefore, can not be exhibited unless the scaly or fibrous powder being used has an aspect ratio of not less than 10. Moreover, the filling amount of the reinforcing filler is adequate to have its extent from 10 to 1,000wt.% against 100wt.% of the organosiliceus-quaoxane oligomer. If the amount is less than 10wt.%, it is impossible to form the skeletal structure of the compound sheet to its perfection with the mechanical characteristic remaining unimproved, and if the amount exceeds 1,000wt.%, the strength of the compound sheet is reduced without having any effect required as the function of a binder. The heatproof limit of the sheet is thus raised.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat-resistant insulating sheet used for insulating materials for electrical and electronic equipment, flexible printed circuit boards, flame-retardant paper, wall covering materials, and the like.

BACKGROUND ART In conventional heat-resistant insulating composite sheets, natural mica or synthetic mica is mainly used as a reinforcing filler, and as an organic binder for forming the sheet, for example, [polyolefin shown in JP-A-48-7073J] , polyvinyl chloride, polyamide, [isocyanate compounds shown in JP-A-52-88141J, "JP-A-57-8259"
Epoxy resins, unsaturated polyester resins, silicone resins, etc. shown in No. 8J are known. Examples of inorganic binders include colloidal silica and colloidal alumina shown in Japanese Patent Publication No. 43-17880J, phosphate glass containing Ba0-P2O3 as a basic component shown in Japanese Patent Application Publication No. 48-70096J, and Showa 57-8259
An aluminum phosphate composition shown in No. 8J is known.

Problems to be Solved by the Invention Compared to the case of inorganic binders, insulating sheets using organic binders do not require much high temperature for curing the binder, and high transparency can be obtained. Also, the electrical properties
It has excellent moisture resistance and flexibility, and is widely used. However, due to the physical properties of the organic material itself used as a binder, it has low heat resistance, and even the most heat-resistant silicone resin or polyimide resin has a maximum usage limit of 4.
It is said to be around 50°C.

However, the demand for heat resistance is becoming increasingly strong, coupled with the demand for higher integration of electrical equipment and higher safety, and there is a strong desire for the emergence of a composite sheet that exceeds the above-mentioned heat resistance limit.

Means for Solving the Problems As a result of various studies in order to improve the heat resistance limit, the present inventor has developed a polyorganosilsesquioligomer thermosetted organosilsesquioligomer as a binder for scale-like or fibrous powder having an aspect ratio of 10 or more. It was concluded that silsesquioxane is optimal, and scaly or fibrous powder with an aspect ratio of 10 or more is added as a reinforcing filler to 100 parts by weight of polyorganosilsesquioxane.
The present invention provides a heat-resistant insulating composite sheet comprising oi parts.

As the reinforcing filler, a scaly powder or fibrous powder such as mica having an aspect ratio of 10 or more can be used.

In the case of scaly powder, the aspect ratio refers to the value obtained by dividing the powder diameter by the thickness, and in the case of fibrous powder, it refers to the value obtained by dividing the length in the long direction of the powder by the width or diameter in the short axis direction.

The types of mica that can be used include natural mica such as muscovite, phlogopite, and biotite, and synthetic mica such as fluorophlogopite.

In addition to mica, other scaly powders that can be used include
Examples include hexagonal boron nitride, graphite, and molybdenum disulfide. Examples of the fibrous powder include alumina fiber, silica fiber, and silicon carbide whiskers. The organosilsesquioligomer used as a binder is represented by the general formula [R1 to R8 are terminals of OH group, alkyl group, phenyl group, OCH group, OC2H5 group, etc.], and is a ladder-type silicone oligomer. It is a thermosetting resin that condenses when heated to form a bridge structure between ladders and become a three-dimensional polyorganosilsesquioxane. It has excellent heat resistance, electrical insulation, arc resistance, weather resistance, flame resistance, etc., and is used for insulating films, protective films, etc.

However, conventionally, the oligomers have only been used as varnishes by dissolving them in organic solvents as paint vehicles, coating vehicles, or binders for molding and lamination.

One possible application that brings out the excellent properties of polyorganosilsesquioxane is to use polyorganosilsesquioxane in the form of a film or sheet as an insulating film or sheet for electrical and electronic parts.
A sheet made by spreading an oligomer varnish into a film and drying and hardening it has almost no flexibility and cannot be used.

By forming a composite sheet of polyorganosilsesquioxane and the above-mentioned mica or other scaly or fibrous powder with an aspect ratio of 10 or more, a heat-resistant insulating composite sheet that is durable and flexible can be produced.

The role of the reinforcing filler is that when the filler is a scaly powder, the wide surfaces of the scales are closely connected, and when it is a fibrous powder, the powders are intertwined to form a skeletal structure and have a reinforcing effect. It is thought that it will come out.

For this purpose, the scaly or fibrous powder used as the reinforcing filler must have an aspect ratio of 10 or more to function, and as a result, the composite sheet will not have high mechanical properties. Although there are cases where it is desirable to increase the aspect ratio, it is difficult to produce a reinforcing filler with an aspect ratio of 300 or more.

The organosilsesquioxane oligomers used as binders are alcohols and esters.

It is soluble in polar solvents such as ketones and aromatic solvents such as toluene, and the varnish that is the solution thereof has a low viscosity, and various organic solvents can be used. When an organosilsesquioxane oligomer is dissolved in an organic solvent to make a varnish, the concentration of the oligomer varies depending on the target thickness of the composite sheet to be created and the type of reinforcing filler, but the preferred concentration range is 10 to 10. If the varnish is less than 1 Ovt, 50%, it is difficult to form a dense coating layer, and if it exceeds 50vt, %, the viscosity of the varnish increases too much, making it difficult to form a uniform coating layer, and making it difficult to handle.

There is no particular method for dispersing the scaly or fibrous powder, which is a reinforcing filler, into the varnish, but it can be dispersed using a general dispersion machine such as a ball mill, vibration mill, media stirring mill, or planetary mill to form a slurry. do it. To make a heat-resistant insulating composite sheet using the slurry obtained in this way,
After spreading the slurry on a releasable film using a doctor blade method, roll coater method, calendar method, etc., it is subjected to a drying process to evaporate the solvent and a heat treatment process to solidify the resin. Obtained by peeling off the film. The heat treatment conditions were 120 to 250°C, 0.1
~40 hours.

In addition to the method described above, a paper-forming method may be used, and a sheet made of only the reinforcing filler may be impregnated with the above-mentioned varnish, spray coated, or roll coated. is also possible.

The thickness of the sheet formed into a sheet by the various methods described above and subjected to curing heat treatment is preferably 20 to 500 μs.

The aspect ratio of the reinforcing filler is preferably 50 or more in the case of a papermaking method, and preferably 20 or more in the case of a coater method such as a doctor blade method or a roll coater method.

In addition, the filling amount of the reinforcing filler is 10 to 100 per part of 100ffiJ of organosilsesquioxane oligomer.
0 parts by weight is suitable; if it is less than 10 parts by weight, the skeleton structure of the composite sheet will not be sufficiently formed and the mechanical properties will not be high; if it exceeds 1000 parts by weight, it will not have the effect as a binder, and on the contrary, The strength of the sheet will be lost.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 Commercially available synthetic mica powder (manufactured by Otake Ceram, average particle size 2
After stirring and dispersing 61H (50 m, aspect ratio +10) in water of 11) for 15 minutes, a wet sheet of 159 mm diameter was made using a standard sheet machine (manufactured by Kumagai Riki Kogyo). The obtained wet sheet is dried in a hot air dryer.
After drying at 105° C. for 3 hours, it was immersed for 15 seconds in a 30% ethanol solution of an organosilsesquioxane oligomer whose side chains were all methyl groups, and then pulled out. The sheet was dried in a hot air dryer at 100°C for 1 hour, and further heat-treated at 150°C for 35 hours.

The thus obtained composite sheet had a thickness of 85 mm and was transparent, had a tensile strength of 1.5 kg/- when measured using a Tensilon measuring machine, and was extremely flexible. In addition, the insulation resistance value is 1. OX was high at 10'Ω·1 or more, and even when water droplets were dropped on the surface, no penetration occurred at all. In addition, the sheet after heat treatment was further heated at 800°C for 1 hour, and the tensile strength and insulation resistance of the sheet were measured.
Each measurement value is 1.5kg/mj, book x 1013Ω
- There was almost no difference compared to (1) before reheat treatment.

Example 2 Commercially available synthetic mica powder (manufactured by Otake Ceram, average particle size 1
0 μ, aspect ratio 40), 200 g of the same was premixed with 600 cc of a 30 vt, % ethanol solution of the same organosilsesquioxane oligomer as in Example 1, and then dispersed for 24 hours in a bot mill with an internal volume of 6 g. The viscous slurry obtained in this way is used as a raw material and is made into a sheet with a doctor blade, dried and heat treated to a thickness of 95mm.
A long sheet with a width of about 210 mm was obtained.

This item is transparent and has a tensile strength of 1.3kg/a+i
It has a high insulation resistance of 1. A high value of more than OX 1013Ω was obtained.

After heating this sheet at 600°C for 1 hour in the same manner as in Example 1, the tensile strength and insulation resistance were 1-2 kg/1, respectively.
+eJ, I×1013 Ω・There was almost no change.

Example 3 300 g of an organosilsesquioxane oligomer whose side chains are 2 methyl groups and 1 phenyl group was added to 57 g of ethanol.
After dissolving in 0cc, average particle size 9-, aspect ratio 2
Add 225 g of hexagonal boron nitride powder of 0.0 ml, pre-prepare for 30 minutes in a lab stirrer, and then place it in an alumina bot mill with an internal volume of 6 g, and form 2.4 j! was added and mixed for 24 hours at 65"p-.

The slurry thus obtained was formed into a sheet using a doctor blade type sheet forming machine with a wet sheet thickness of 150 fi, and after curing at 150° C. for 35 hours, a sheet with a film thickness of 57 mm was obtained.

This sheet was flexible, and when the tensile strength was measured, it was as high as 1.8 kg/-.

Examples 4 to 7 Using the same ethanol solution of organosilsesquioxane oligomer as in Example 3, as a reinforcing filler, synthetic mica powder (average particle size 20Hn, aspect ratio 50),
Alumina fiber (fiber diameter 9Itm, aspect ratio 25),
Alumina/silica fiber (fiber diameter 3.

When a silicon carbide whisker (aspect ratio 40) and a silicon carbide whisker (fiber diameter 2, aspect ratio 30) were used independently, sheets similar to those in Example 3 were made and properties were evaluated, and the results shown in Table 1 were obtained.

Table 1 Comparative Example The same ethanol solution of organosilsesquioxane oligomer as in Example 3 was used as a filler, and 20 g of hexagonal boron nitride as in Example 3 was added to form a sheet.
It had no flexibility.

Effects of the Invention When mica is used as a reinforcing filler, the heat-resistant insulating composite sheet of the present invention maintains high transparency, flexibility, and water repellency, and has a heat resistance limit of 500°C or higher and a maximum temperature of 600°C.
℃, and the aspect ratio of non-micas is 1.
Even when a filler of 0 or more is used, the transparency is inferior to that of mica, but other properties are not impaired, and it can be used for insulation of single layer wires and barriers of transformers, and conductor insulation of high-voltage motors and generators. This makes it possible to use and apply sheets that require heat-resistant insulation, such as .

Claims (2)

[Claims] (1) A heat-resistant insulating composite sheet comprising 10 to 1000 parts by weight of scale-like or fibrous powder having an aspect ratio of 10 or more as a reinforcing filler to 100 parts by weight of polyorganosilsesquioxane. (2) The heat-resistant insulating composite sheet according to item 1, wherein the reinforcing filler is natural mica or synthetic mica powder.